LONDON — The owner of Britain’s Alton Towers amusement park has been fined 5 million pounds ($6.5 million) for a roller coaster crash that left five people seriously injured.

Two victims had to have legs amputated after two cars on the Smiler ride collided in June 2015. An investigation found that an operator had overridden the roller coaster’s governing computer system.

Merlin Entertainments Group, which owns the park 150 miles (240 kilometers) north of London, admitted breaches of health and safety rules at a hearing earlier this year.

Judge Michael Chambers says in Tuesday’s judgment that a “catastrophic failure” of basic safeguards caused “a needless and avoidable accident.”

Merlin chief executive Nick Varney said the company was determined that such an accident would never happen again.