A surgery patient fell into a coma in mid-May at Tokyo Medical and Dental University Hospital due to suspected malpractice, informed sources said Friday.

The sources did not disclose the name or gender of the patient, saying only that the case involved someone in their 20s who underwent surgery in May at the hospital, which is located in Tokyo's Bunkyo Ward. The patient temporarily stopped breathing after being administered a sleeping drug on May 14, the sources said.

It is suspected that a doctor misinformed nurses about the dose of the drug, which the doctor administered to help the patient rest, the sources said.