LONDON — Richard Huckle, who was serving 22 life sentences after admitting to the sexual abuse of scores of children, was found dead under “suspicious” circumstances in prison, according to the police, who said on Monday that they were investigating.

Mr. Huckle, 33, was stabbed to death with a makeshift knife after being attacked in his prison cell, according to local news outlets, but officials declined to confirm the circumstances.

Mr. Huckle was given 22 life sentences in June 2016 after admitting to 71 offenses against children between the ages of 6 months and 12 years, the BBC reported at the time.

Image Richard Huckle Credit... National Crime Agency, via Agence France-Presse — Getty Images

He died at Full Sutton prison, near York, according to a statement by the Humberside Police.

A police investigation was underway, the Ministry of Justice said in a statement on Monday, and the police said they were “treating the death as suspicious.”