DURHAM, N.C. (AP) -- One patient has been killed and three others suffered slight injuries in an explosion at Durham Regional Hospital in central North Carolina early Tuesday.

No one else was hurt in the explosion on the hospital's sixth floor around 2:15 a.m., said Katie Galbraith, hospital chief of operations.

Officials were trying to determine exactly where the explosion occurred, Galbraith said.

The hospital's sprinkler system worked properly and the fire was controlled as about 30 firefighters arrived, Galbraith said. Other patients in the unit, a separately licensed facility operating as Select Specialty Hospitals, were moved to other parts of the hospital.

Some other patients were moved because of flooding caused by the sprinklers.

They are safe and they are being well cared for, Galbraith said.

The three slightly injured patients all had been on ventilators prior to the explosion. They were taken to the emergency room to be checked for smoke inhalation and then sent to the intensive care unit.

The names of the victim and those injured were not immediately released.

Galbraith said the hospital staff practices for just such emergencies.

Our focus is on making sure people are safe, she said. They did exactly what they're trained to do.

Durham Regional is a 369-bed acute care hospital.

© 2012 THE ASSOCIATED PRESS.