Alton Towers gates shut for a second day

Alton Towers theme park will stay closed until the cause of a rollercoaster crash is discovered.

The attraction's gates are shut for a second day while Health and Safety experts investigate what happened.

Nick Varney, chief executive of Merlin Entertainments, which runs the park, said it could only reopen when the investigation had finished.

What happened?

Four people were seriously hurt in the collision on 'The Smiler' ride on Tuesday.

They were taken by helicopter to hospital.

Officials are trying to work out how it happened and how to keep people safe in the future.

Officials say one of the carriages with 16 people on it, crashed into another, empty carriage on a low section of the track.

People were trapped on the ride for more than four hours following the crash

Nick Varney, head of Merlin Entertainments, thanked the emergency teams and apologised to those affected and their families.

He said: "This has been a terrible incident and a devastating day for everyone here.

"We have a very strong record of safe operation of our rides here at Alton Towers and it is our priority."

Very rare

Rollercoaster crashes like this are incredibly rare.

The International Association of Amusement Parks and Attractions say that the chance of being injured on an amusement park ride is one in 24 million.

It's not known when the investigations will finish or when the park will reopen.