TOYAMA (Kyodo) Police have begun investigating the deaths of seven patients from 2000 to 2005 at a hospital in Imizu, Toyama Prefecture, as potential homicides because the patients died after the head of surgery removed their respirators, the city government and police said Saturday.

The head of the Imizu City Hospital, Hidetsugu Asanoi, said the 50-year-old surgeon said he removed the respirators of the seven, five of whom suffered from cancer, with the consent of their families but not of the patients themselves.

"Although I don't know if (the surgeon's acts) constitute criminal acts, I feel they were morally problematic," Asanoi said at a press conference.

The surgeon has said he removed the respirators for the sake of the patients and that their deaths were "dignified deaths," according to Asanoi.

The seven -- all Toyama Prefecture residents -- consist of four men and three women aged from about 50 to over 90, he said.

Toyama police said they have been cautiously investigating the cases and questioning the people concerned.

At a new conference, Imizu Mayor Shizuo Bunke said the city has begun its own investigation and found an "unnatural" case where the same surgeon attempted to remove the respirator of another patient, a 78-year-old man.

The surgeon was quoted as telling Asanoi in October that he wanted to remove the man's respirator. Asanoi, who was suspicious, rejected the request and set up an in-house investigation team, the mayor said. The man's respirator was not removed.

The surgeon is to leave the hospital at the end of March.

The city has filed a complaint on the case with the Toyama Prefectural Police.

"I have never heard of bad rumors about the hospital. I hope this is not true," said a 70-year-old resident.

Imizu City Hospital was founded in 1950.