Photo/Illutration An ambulance overturns in Akishima, western Tokyo, in December. (Provided by a reader)

An ambulance that hit a center divider and overturned last month was driven by a paramedic who became drowsy after working for around 17 hours straight, the Tokyo Fire Department said on Jan. 17.

The accident occurred on a national route in Akishima, western Tokyo, around 1:50 a.m. on Dec. 29 amid a surge in emergency calls from COVID-19 patients, investigative sources said.

No patient was aboard the ambulance, which had just transported a patient to a hospital and was heading back to the fire station.

The three paramedics in the vehicle, including the driver, were taken by another ambulance to a hospital with minor injuries.

Footage from an onboard camera showed the driver and a paramedic in the passenger seat nodding off when the ambulance hit the center divider on the road, the sources said.

“The driver became drowsy,” the fire department said in a statement about the internal investigation.

The three paramedics came to work at 8:30 a.m. on Dec. 28 and started their shift at 9 a.m.

They were on duty for roughly 17 hours without a break from their first dispatch to 1:50 a.m. the following day, when the accident occurred, according to the fire department.

The paramedics were dispatched seven times over that period, and each case took an average of about two hours or more to transport the patients to hospitals.

Officials said they believe the accident was caused in part by the increase in emergency calls during the latest spread of the novel coronavirus.

COVID-19 patients are filling up hospital beds in Tokyo and elsewhere, so it also takes more time for ambulance attendants to find hospitals that can accept other emergency patients, the fire department said.

“We take this incident seriously, and we will make efforts with all fire departments to prevent a recurrence, including reviewing the emergency service system,” the fire department said in the statement.

During the week through Jan. 15, 52 firefighting headquarters in large municipalities nationwide reported 8,161 cases in which it was difficult to find hospitals to accept emergency patients due to the strained conditions from COVID-19, according to the Fire and Disaster Management Agency of the internal affairs ministry.

That figure was a record high for the fourth week in a row.