LONDON — A teenager was arrested on suspicion of attempted murder after a 6-year-old boy was thrown from Tate Modern museum in London on Sunday, the Metropolitan Police said.

The child was tossed from the 10th-floor viewing platform and landed on the fifth-floor roof, the police said in a statement. The victim was treated at the site and then airlifted to the hospital in critical condition.

The police said a 17-year-old male suspect was arrested on the same viewing platform.

“There is nothing to suggest that he is known to the victim,” the police said.

The episode led to the lockdown of the renowned museum; some visitors said on social media they felt trapped inside, and others said they were turned away.