DEVELOPING STORY: EL SEGUNDO, Calif.--A helicopter crashed into a building in El Segundo, Calif. Sunday morning. 

While lifting an air conditioning unit from the roof of the Raytheon Company Space and Airborne Systems Building, the helicopter, which was reportedly tied to equipment, came down alongside the building, catching fire to its first and second floors, according to sources. 

The three-alarm fire was subsequently extinguished by firefighters. 

The pilot was injured and transported to Harbor UCLA hospital, where he is in stable condition.

The Federal Aviation Administration (FAA) and the National Transportation Safety Board (NTSB) have been contacted to evaluate the scene, sources added.

No other injuries have been reported.