A powerful explosion in the Turkish capital collapsed two stories of a construction machinery factory on Thursday, killing at least three people, injuring some 30 others, and leaving several people trapped under debris, an official said, according to AP. Fethi Yasar, mayor for the area, said a few people were believed to be trapped, and search and rescue teams has arrived at the scene in an industrial area of the city to help them out. Yasar said around half the 80 workers of the factory escaped unharmed. The explosion ripped off the building's glass-covered facade and shattered neighboring buildings' windows. Twisted metals and concrete slabs were strewn around the area. NTV news channel showed medics and passers-by helping an injured man lying on the pavement outside the four-story building. It showed medics helping another injured person onto an ambulance. One witness told NTV television he saw dozens of people covered in blood lying on the ground before the ambulances arrived at the scene. The cause of the explosion was under investigation, but Ankara's Mayor Melih Gokcek told CNN-Turk television that the blast was most likely started by oxygen tanks at the factory. He did not give details.