A fire that broke out in a Lakewood apartment complex early Monday injured three people and displaced up to 40, according to West Pierce Fire & Rescue.

The blaze started about 2 a.m. at the Pacific Ridge apartments in the 13000 block of Lincoln Avenue Southwest.

Neighbors pounded on each other’s doors to alert others about the fire.

When fire crews arrived and found flames coming from several units, they upgraded to a second-alarm fire and evacuated all residents.

Three injuries were reported. Two of them were minor and treated on scene. One man was taken to an area hospital with serious injuries.

At least five apartments were seriously damaged in the blaze, with seven to 11 other units damaged by smoke.

Investigators have not determined what caused the fire.

The Red Cross responded and is helping about 16 families find temporary housing.