Seven people have died in an accident at South Side Children’s Hospital in Boston, the hospital’s chief executive said on Tuesday.

The accident on Tuesday morning at the south shore hospital, the city’s largest, occurred while patients were being transported to other hospitals, said Chief Medical Officer Dr. Christopher McKeown.

The victims were being transferred to the hospital after being admitted to a medical center for a chest condition, he said.

It’s not clear whether they were being treated for a heart attack or a cardiac arrest.

McKeown said the hospital was doing everything it could to identify the cause of the accident and get all of the patients home.

“We are taking every possible step to get them home safely,” he said in a statement.

A spokesman for the Massachusetts State Police declined to comment.

The hospital said the accident occurred on Tuesday at 2:15 p.m.