Alton Towers will remain closed until the cause of a roller coaster crash which left 16 people injured is discovered, the theme park’s chief has said.

The attraction’s gates are shut for a second day while the Health and Safety Executive looks into why two carriages collided on the Staffordshire venue’s ride, The Smiler, at around 2pm on Tuesday.

Nick Varney, chief executive of Merlin Entertainments, which runs the resort, said the park could only reopen when the investigation had concluded but did not give a time-frame.

Writing in the Sun, he said: “At this point I don’t know if it was a technological or a human error. We want to know if this issue is isolated to The Smiler. We can’t open again until we’re sure.”

A total of 16 people were hurt - including two men aged 27 and 18, and two women aged 19 and 17, who suffered serious leg injuries.

An Alton Towers spokesman said: “The decision has been taken that Alton Towers theme park will remain closed on Thursday following the incident on The Smiler.

“Guests with pre-booked tickets and those arriving at the theme park will have the choice of a full refund or an alternative dated ticket.

“Guests with pre-booked tickets have the option to use their tickets tomorrow at an alternative attraction. See website for more info.”

The £18 million roller coaster, which boasts a world record 14 loops, has been closed twice because of safety concerns since opening two years ago.

In July 2013 it was closed after reports that a bolt was seen to have fallen from the ride and in November that year the roller coaster was closed after plastic guard wheels came loose and hit front-row riders.