Police began a full investigation Saturday into the case of a doctor who performed euthanasia on a comatose man.
The incident occurred at Kawasaki Kyodo Hospital in Kanagawa Prefecture in 1998.
Police sources say they are considering arresting the female doctor on suspicion of murder for administering a muscle relaxant that caused the man's death. The patient has not been identified.
The comatose man, in his 50s, was admitted to the hospital in early November 1998, hospital officials said at a news conference Friday. He died in mid-November after the doctor removed a tracheal tube and administered the muscle relaxant.