MARBLEHEAD – A fire official said a roof collapse at a downtown strip mall Tuesday morning damaged several businesses but caused no injuries.Meanwhile, the town and building owner are trying to find out why the roof collapsed and whether the building may have to be torn down.”We’re not sure (as to the cause), there wasn’t a lot of snow on the roof,” said Marblehead Fire Capt. Scott Murray.Murray said firefighters responded to the Walgreens on Pleasant Street across from the monument at about 8:30 a.m. Tuesday and saw that the roof in the store was bowed in. The roof totally collapsed about two hours later and damaged walls in the adjacent Starbucks and a branch of the Salem Five bank. The 7-Eleven was not believed to have been affected, Murray said.”There was nobody hurt – everyone was evacuated,” he said.He reported that the property owner and representatives of the town building department are evaluating the damage, and the businesses were roped off Tuesday evening.Murray said the building might be a total loss and have to be torn down, but town officials are still determining the extent of the damage and what caused the collapse.