A three-alarm fire broke out in a Queens Laundromat yesterday, injuring two civilians and 19 firefighters, authorities said.

The blaze started at 2:55 a.m. in the first floor of a building on 45th Avenue in Flushing and raged for three hours before firefighters were able to rein in the flames, said a spokesman for the FDNY.

Two civilians were in serious condition and were taken to an area hospital, authorities said.

Their injuries were not considered life-threatening.

Nineteen firefighters were also injured, although two refused medical attention, said the FDNY spokesman.

The fire was brought under control at about 5:55 a.m., officials said.

The cause of the fire was not immediately known.