Media playback is unsupported on your device Media caption Nick Varney said extra safety protocols had been introduced at its parks

Four rollercoasters at three theme parks have been shut after a crash at Alton Towers in which 16 people were injured, four seriously.

The Smiler, which crashed, and Saw, a similar ride at Thorpe Park, would both be shut "for the foreseeable future", owner Merlin Entertainments said.

Two rides at Chessington World of Adventures have also been closed until new safety protocols have been applied.

Merlin Entertainments said the victims of the crash would "want for nothing".

Two carriages, one of which was empty, crashed on Tuesday, leaving some passengers trapped for four-and-a-half hours.

Two men, 27 and 18, a woman, 19, and a girl, 17, suffered serious leg injuries and remain in hospital.

'Criminal prosecutions'

Daniel Thorpe, 27, from Buxton underwent surgery on Thursday, the BBC understands.

Vicky Balch, 19, from Leyland in Lancashire, remains in a "critical condition" in hospital, according to her lawyer Paul Paxton.

Image copyright facebook Image caption (L to r) Daniel Thorpe, Vicky Balch, Joe Pugh and Leah Washington remain in hospital following Tuesday's crash

Ms Balch is expected to make a claim for damages, Mr Paxton said, although the main focus at the moment was on her recovery.

"It is expected that serious consideration will be given to criminal prosecutions. The family are distraught that a fun day out could turn into such a potentially life-changing disaster," he said.

Nick Varney, chief executive of Merlin Entertainments, said it was the "first major accident we've had on a ride in the company's history".

'Want for nothing'

"Our first priority has been to look after the people on that ride," he said.

Media playback is unsupported on your device Media caption Merlin Group has closed three more theme park rides, as Judith Moritz reports

"We want to do everything we possibly can to support those families [most severely affected].

"We haven't managed to make contact with all of them and we are desperately trying to do that.

"They will want for nothing in the sense of what they need, be it accommodation, transport anything.

"And of course there will not be any question of them needing to go through the anguish of arguing for compensation."

'Cause of failure'

Alton Towers will remain closed on Saturday, but bosses hope to reopen the park in the "next few days". The Smiler ride will stay out of action until the cause of the accident is known.

Health and Safety Executive (HSE) inspectors have served a prohibition notice on the ride stopping its use "until action is taken to deal with the cause of the failure".

Image copyright PA Image caption Thorpe Park's Saw is one of the rides that has been shut

Mr Varney said there was "no conclusive answer yet", but the firm believed the accident was caused by a "rather unique sequence of events".

It is estimated the park has been losing up to £500,000 a day since Tuesday.

Sam Bailey, 30, from Kent, said she had been in the same row of the Smiler ride only a few days ago as those injured.

"By chance I was sat on the front row of the carriage" she said.

"It's crazy to think after seeing the pictures. I happened to be sitting on the same seat as them only a few days earlier."

'Safety protocols'

Ms Bailey was also at Chessington World of Adventure in Surrey on Thursday and said the Dragonsfury ride was shut down soon after 15:00 BST.

The park's Rattlesnake ride is also closed.

Mr Varney said extra safety protocols had been introduced across Merlin's theme parks, but it would take a few days to implement those on two Chessington rides as they used "different operating systems".

He said Thorpe Park's Saw ride had been closed until the cause of the Alton Towers crash is known as it was made by the same manufacturer and was essentially a "very similar ride" to the Smiler.

Image copyright Ben Richardson Image caption Sixteen people were in one of the carriages that crashed at Alton Towers, the other was empty

Merlin Entertainments said it was co-operating fully with the HSE investigation and intended to complete a "thorough appraisal" of its safety processes at Alton Towers "in the near future".

The HSE said carriages involved in the Smiler crash would be removed later and taken to its laboratory in Buxton for further analysis.

It said the prohibition notice did not affect other rides at Alton Towers.