The Smiler Alton Towers
Four people were seriously injured at Alton Towers after a carriage full of people collided with an empty one West Midlands Ambulance Service

The owner of Alton Towers has closed three additional rollercoasters at two other resorts following The Smiler crash, which left four people seriously injured.

Merlin Entertainments said it will now shut down Thorpe Park's Saw ride as well as rollercoaster rides Dragon's Fury and Rattlesnake at Chessington World of Adventures for the "foreseeable future" while inquiries continue into the collision at Alton Towers.

The Smiler ride at Alton Towers has been shut since the accident.

Four people – Daniel Thorpe and his girlfriend Vicky Balch and Joe Pugh, 18, and his girlfriend Leah Washington, 17 – were left seriously injured after a full carriage on the £18m rollercoaster crashed into an empty one.

Thorpe Park's saw ride is based on the popular horror francise Getty

Alton Towers has been closed for three past three days and will remain closed for a fourth (6 June) while the resort investigates what caused the collision.

Merlin's chief executive, Nick Varney, said: "This has been a terrible experience for everyone involved and one we sincerely regret. Our thoughts remain with those who were seriously injured and we are doing everything we can to support them through this difficult time. It is an accident that should not have happened, and we are determined that it will never happen again.

"While the investigation into the causes is continuing, we have identified a series of additional safety protocols that we are implementing immediately across our multi-car rollercoasters. These will act as an additional safeguard to further strengthen our operating and safety standards. This has been a devastating experience, and we are committed to learning the lessons from it."

A spokesperson for Merlin added: "The safety of our visitors is our fundamental priority. We have a strong safety record at Alton Towers and across the Merlin Group.

"Today we are enhancing our safety standards by issuing an additional set of safety protocols and procedures that will reinforce the safe operation of our multi-car roller coasters.

"These are effective immediately."

It has since emerged Alton Towers did not call emergency services until 11 minutes after the Smiler rollercoaster crashed, contradicting previous reports that the resort "called immediately".