Story highlights The fire started on the first floor and quickly spread

The cause is under investigation

(CNN) A fire at a hospital in Saudi Arabia has killed at least 25 people and injured 123 others, the Civil Defense said.

The fire broke out early Thursday morning at the Jazan General Hospital in the southern coastal city of Jazan, said Civil Defense spokesman Maj. Yahya al-Qahtany.

Firefighters search the hospital after the fire.

It started on the first floor, which houses the nursery, the maternity ward and the critical care unit.

The smoke quickly spread throughout the four-story building.

The cause of the fire is under investigation.