Police have arrested Satoshi Uematsu, a 26-year-old former employee at the facility in Sagamihara, Kanagawa Prefecture, about 25 miles (40 km) southwest of Tokyo, a Kanagawa prefecture official said. Uematsu had turned himself in, the official told a news conference carried on public broadcaster NHK.

While all 19 had not yet been officially declared dead, they were all “in a state of cardiac arrest”, the official said. Another 25 people were wounded, 20 of them seriously, he said.

Japanese officials often describe people as being in cardiac arrest before they are officially declared as dead.

The Kyodo news agency says the dead ranged in age from 18 to 70 and included nine males and 10 females. Earlier media reports had said as many as 45 people had been wounded.

Staff called police at 2.30 a.m. local time (1730 GMT Monday) with reports of a man armed with a knife on the grounds of the Tsukui Yamayuri-En facility, media reported. The man wore a black T-shirt and trousers, reports said.

The 3-hectare (7.6 acre) facility, established by the local government and nestled on the wooded bank of the Sagami River, cares for people with a wide range of disabilities, NHK said, quoting an unidentified employee.

Another woman who said she used to work at the facility said many patients were profoundly disabled.