Here's Hillary Clinton and Donald Trump reacting to the news of the explosion.

Deborah Griffith is another eyewitness to the explosion. 

Eyewitness Itay Cohai says there was a "huge explosion" and that he heard screaming immediately afterwards.

Presidential candidates Hillary Clinton and Donald Trump have also been briefed on the explosion. 

Mrs Clinton said: "We need to do everything we can to support our first responders. Also, to pray for the victims. 

"We have to let this investigation unfold... I'll have more to say about it when we actually know some facts." 

Mr Trump said: "We better get very tough. We'll find out. It's a terrible thing that's going on in our world and in our country and we are going to get tough and smart and vigilant. We'll see what it is."

Image source, AP

President Obama has been briefed on the New York explosion, according to officials. 

"The president has been apprised of the explosion in New York City, the cause of which remains under investigation," a White House spokesman said. 

"The president will be updated as additional information becomes available." 

Mr Obama is due to travel to New York on Sunday and stay in the city for several days, to attend the United Nations General Assembly.

Itay Cohai was at his friend's apartment when he heard the blast in Chelsea. 

Law enforcement officials in New York say that the device found at the second Chelsea location appeared to be a pressure cooker attached to wiring and a mobile phone.  

It has been safely removed, and while we know few details about the device, pressure cooker bombs can cause serious damage.

David McKay, who lives near to where the explosion happened, says people were shocked but the incident will not have a long-term impact on how they live their lives.  

Shortly before the explosion in New York, eight people were injured in a stabbing attack at a Minnesota shopping mall.

The incident, which was reported about 20:15 (12.15 GMT), ended with the suspected attacker, who was dressed in a private security uniform, being shot dead by an off-duty police officer. 

St Cloud police chief Blair Anderson said none of the injuries were life-threatening, and that the suspect referenced Allah during the attack, asking at least one person whether they were Muslim. 

However, he did not call the attacks an act of terrorism, saying the man's motive is not yet known.

Mayor of New York, Bill de Blasio, said that "all hands are on deck" in the city.

"We also want to be up front in saying that there is no evidence at this point of a terror connection to this incident," he added.

AP is reporting that a police official in New York said the explosion appears to have come from a construction toolbox in front of a building.

To recap the news so far:

• An explosion in the Chelsea district of New York has injured 29 people, one seriously
• A device found a few blocks away from the explosion was removed by a robot
• Mayor Bill de Blasio describes the explosion as a "very bad incident" but says there is no "credible and specific threat at this moment"

Image source, AP

The scene of the explosion was the Chelsea area of New York, which is among the most fashionable districts of Manhattan. 

Mayor de Blasio has described the injuries suffered by those injured in the explosion as "significant but at this point we can confirm that none of those injured are likely to die".

Nick Bryant
BBC New York Correspondent

Both CNN and the Associated Press are reporting that the second device, which has now been removed, appeared to be a pressure cooker attached to wiring.

CNN has tweeted a photo of what is says is the device.

Mr de Blasio also said there was no evidence of a link to a pipe bomb explosion in neighbouring New Jersey hours earlier.