“When the police arrived they were trying to force open the wall,” Mattias Skarp at Dalarna police told news agency TT.

“Staff saw what was happening and they called us. We then maintained telephone contact and they could then relate the chain of events. We were on the scene within ten minutes and were able to arrest two people.”

Staff at the hospital were busy preparing to move to another department of the hospital in the event that anybody had been able to force their way in.

Mattias Skarp told news agency TT that the police have a good idea of who the target of the escape attempt was although said that information is still being collected.

The two people arrested, a man and a woman both in their thirties, are previously known to the police.

“The area has been sealed off and a forensic examination will be conducted during the course of the day; we will also get in contact with the prosecutor,” Skarp said.

The alarm call that an escape attempt was underway prompted a massive police operation.

A police helicopter was called in from Stockholm, but returned home shortly after. Police forces in Gävle were also put on alert but later told to stand down.

The Säter hospital was opened in 1912 and was at the time Sweden’s largest mental hospital.