At least 25 people have been killed and 107 injured in a fire at a hospital in Jizan, Saudi Arabia, authorities said.

The Saudi civil defence directorate said in a post on Facebook that the fire at the Jizan General Hospital started at about 2.30am local time.

It is not yet known what caused the blaze, which began on the first floor of the hospital.

The intensive care unit and maternity ward are both on the first floor.

Saudi Arabian authorities are on the scene investigating.

At least 20 brigades from the civil defence directorate were deployed to fight the blaze, which has now been brought under control.

Dr. Ahmad Alsum, an emergency doctor at Jizan's King Fahd Hospital, told Al Jazeera that most of those injured in the fire were patients.

Patients were transferred to a number of other nearby public and private hospitals.

Alsum said early indications were that the blaze was an electrical fire.

"Twenty-five people died in this fire. It is very devastating," he said.

Jizan is the capital of the Jizan region in southwest Saudi Arabia, located immediately north of the Yemen border.

Al Jazeera