Canada's Transportation Safety Board says it is launching an investigation after the implosion of the Titan submersible left all five passengers dead
In the US, a separate probe will be launched involving the American counterpart and US Coast Guard
Tributes have been paid to Hamish Harding who would have turned 59 on Saturday, Shahzada Dawood, 48, and his son Suleman Dawood, 19, Paul-Henri Nargeolet, 77, and Stockton Rush, 61
Emails seen by the BBC show that concerns from an expert over the safety of the Titan sub were dismissed by OceanGate CEO Rush in 2018
Other industry experts have also raised questioned following the "catastrophic implosion"
But an OceanGate investor who has made the trip down to the Titanic told the BBC that the idea Rush had done anything wrong was "disingenuous"
It's emerged the US Navy originally detected “an acoustic anomaly consistent with an implosion” shortly after the Titan lost contact on Sunday
The update has now turned towards what food and drinks would be left for the crew in the missing sub.
Capt Frederick says: "They do have limited rations aboard but I can't tell you exactly how much."
A reporter has asked about a reported rectangular object which was spotted, but Capt Frederick said the aircraft crew that saw the object yesterday determined it not to be part of the case.
He said it is not uncommon to spot various objects in the ocean that are not part of a search.
Next up Capt Frederick takes some questions from reporters - the first one is about the reported noise recorded yesterday.
He admits they don't know what it is and that is why they have put so many sonobuoys in the area.
Capt Frederick hopes more ROVs will arrive in the morning as they continue to search the area where the noise was detected.
Some of those extra ROVs have extra depth capability, he tells reporters
Captain Jamie Frederick said that yesterday the Canadian P-3 detected underwater noises in the search area.
“As a result ROV operations were relocated in an attempted to explore the origin of the noises. Although the ROV searches have yielded negative results they continue."
He added that the data from the P-3 aircraft has been shared with US Navy experts for further analysis "which will be considered in future search plans".
The US Coast Guard currently have five surface vesels searching for the Titan and they expect there to be 10 in the next 24 hours.
There are two Robotically Operated Vehicle (ROV) and there should be additional ROVs joining the search.
More from Capt Frederick who says the area of the search has expanded - as he says the surface search is now twice the size of Connecticut, and the sub-surface search is approximately 2.5 miles deep.
He says officials and rescuers are having to factor in sea changes and currents.
"There is an enormous complexity of it being so far offshore," he adds.
The press conference has just started.
Captain Jamie Frederick of the US Coast Guard is introducing several experts who are there with him.
He admits it is an "extremely difficult" time for friends and family of those trapped in the sub.
"We remain in close contact with the family," he says.
We are expecting the press conference from the US Coast Guard to start in the next few minutes.
Here's the scene in Boston as members of the media wait to hear the latest update.
You can watch the live stream by clicking the Play button at the top of this page.
Image source, MoD/Crown Copyright/PA WireLockheed P-3 Orion was used before in the underwater search for the Malaysia Airlines flight MH370
Here are three of the vehicles and vessels being used in the search:
P-3 aircraft:
Remotely Operated Vehicle (ROV):
Victor 6000 :
The US Coast Guard will share the latest on the search in 30 minutes, at 18:00 BST.
Captain Jamie Frederick, the First Coast Guard District response coordinator, will provide an update on the ongoing effort to find the missing submersible.
Stay with us for updates. You'll be able to stream live at the top of the page.
David Marquet, a retired US Navy captain, says he admires OceanGate’s innovative spirit but wonders if they went "a little too far".
Captain: 'OceanGate might have gone too far'
Image source, SUPPLIEDShahzada Dawood (top) and Hamish Harding (bottom) are among the five people on the Titan
If you're just catching up on this story, here's a quick reminder of who the five passengers onboard are:
We've been getting more updates about the different vessels that have been joining the search efforts.
The US Coast Guard has said this afternoon that at least eight more ships have started arriving at the search site.
Some of the new vessels include:
The new ships will also join the Polar Prince, which is still there after deploying the Titan submersible on Sunday, as well as Deep Energy, a pipe-laying vessel flagged in the Bahamas, and three other Canadian vessels.
"It's a good combination," Matthew Heaslip, a senior lecturer in naval history at the University of Portsmouth, told the New York Times.
"A mix of vessels that would be very much intended for this kind of rescue."
Pallab Ghosh
Science correspondent
Image source, .We heard this afternoon about the arrival of a French underwater Robotically Operated Vehicle (ROV), the Victor 6000.
Its role will be to search for the Titan and to remove any obstacles that are stopping it from floating to the surface.
It will take two hours to prepare the ROV once it arrives and the operation is likely to take several more hours – and time is not on the side of a rescue operation.
But the head of the organisation that operates the Victor 6,000, Jan Opderbecke, of the French Research Institute for Exploitation of the Sea, told BBC News that “where there is still hope, we have to try”.
Nadine Yousif
Reporting from St John's
Last night, two C-17 US military planes arrived in St John’s in Canada at 19:30 local time (23:00 BST) with supplies for the search and rescue mission. Another one is scheduled to arrive later on Wednesday.
A 747 is also on its way, carrying equipment to aid with the search, the US Coast Guard says.
Cranes were loaded onto a Horizon Arctic ship late Tuesday night, which was docked in the harbour of St John’s.
It has since departed, along with two other Canadian Coast Guard ships, to the site of the Titanic wreckage. The ships arrived on Wednesday morning, according to the US Coast Guard.
The fog in St John’s from yesterday has since cleared. Out in the mid-Atlantic, winds are traveling at 23mph with a temperature of around 10 C (50 F).
More from Mauger now. He describes the search as "complex" and difficult", adding that it is being conducted in a remote location some 900 miles off the coast of Cape Cod in Massachusetts in the US.
"This has happened in a remote location, we have prioritised our efforts both on surface and subsurface search," he said, and added that they were working very closely with the acoustics experts to understand the noises they are hearing.
Experts and equipment have indicated "that noise is potentially being generated" by occupants of the sub and as a result they relocated remote operated vehicles (ROVs) on sight.
But they still have no confirmation on what the noise is.
"We've picked up noise signatures and we are working through the analytics of that."
When BBC Science Correspondent Jonathan Amos asked if there were plural noises, Mauger confirmed, saying "there were a number of signatures."
Rear Admiral Mauger said that based on information that the operator had initially provided, the sub had approximately 96 hours when they first cut connection.
As for why it is a difficult calculation to predict he said one reason is that it's based on consumption of the occupants:
"One of the factors that makes it hard to predict how much oxygen is left is that we do not know the rate of the consumption of oxygen per occupant on the sub."
He said the search team is operating under the assumption that they have about 20 hours left to find and rescue the sub, which is sometime tomorrow morning local time.
Rear Admiral John Mauger from the US Coast Guard has just told BBC News that the crew on board the Titanic submersible may have less than 20 hours of oxygen left, based on the initial estimate of 96 hours.
He says it is hard to determine exactly how long they have, due to various factors, but time is running out.
Pallab Ghosh
Science correspondent
We're going to answer a few more questions that have been sent in.
Kevin from North Carolina asks why the submersible doesn't have GPS pinging equipment like an aeroplane's black box?
GPS does not work deep underwater. And it is thought that there has been a failure in what communications equipment is on board.
Here's an explanation of how sonar buoys may be picking up the sounds of tapping inside the sub.