LONDON (AP) — Four people were found stabbed to death Monday at a home in south London, British police said. A man has been arrested.

The Metropolitan Police force said officers were called by neighbors to reports of a disturbance at around 1:40 a.m. and forced their way into a home in the Bermondsey area. Inside they found three women — in their 30s, 40s and 60s — and a man in his 60s “suffering what are believed to be stab injuries.”

All four were pronounced dead at the scene.

A fifth man, in his late 20s, was detained on suspicion of murder. Police said the victims and the suspect all knew one another and they were not looking for other suspects.

Polices said they were still contacting the victims’ families, and did not release their identities.

“Such terrible events are rare, but I know that will not diminish the shock that will be felt across London and the wider country,” police Chief Superintendent Colin Wingrove said. “I assure you, this investigation will leave no stone unturned in discovering the facts.”