The FDNY is investigating the cause of a two-alarm fire Monday night in Harlem that left more than 20 people injured.

Flames broke out around 7 p.m. inside the Martin Luther King Houses on Fifth Avenue near 112th Street.

Flames started spreading in a trash compactor on the 10th floor, sending heavy smoke through the building.

Seven fire fighters suffered minor smoke inhalation, while seven residents were taken to nearby hospitals.