BAGHDAD, Iraq - An explosion leveled part of a building as U.S. troops were raiding it in northern Baghdad today, wrecking four Humvees and wounding at least one soldier and several Iraqis.

The cause of the explosion was not yet known. Witnesses said it came after U.S. troops broke in to search the building, which residents said housed a weapons repair shop.

The blast leveled the front part of the one-story building, in the Waziriya district, and set four Humvees outside on fire. Later, Iraqis dragged one of the Humvees away, looted it, and set it ablaze again.

The condition of the American and the Iraqis was not known, nor was the total number of casualties.

At least one wounded U.S. soldier was seen in footage from Associated Press Television News being taken away on a stretcher from the burning Humvees. Witnesses reported as many as 10 Americans being loaded into ambulances.

Several Iraqis were seen in APTN video being carried out of the rubble. A woman was weeping as she was carried out of the ruins over a man's shoulder. Another victim, a young man, appeared unconscious as Iraqis brought him out by his legs and arms

.

Hours later, dozens of teenagers were looting the burned Humvees. A fire engine was still extinguishing a fire rising from the rubble.

Some neighbors reported a perfume shop was housed in the building, but others said it once held a scrap metal workshop where weapons were repaired and used ammunition recycled.

A military spokesman said the blast destroyed a number of Humvees but had no details.