U.S. State Department officials say the explosion that injured at least seven people Thursday at a hotel in Islamabad, Pakistan, was probably caused by a bomb.
The U.S. officials point out, however, that the explosion at Islamabad's Marriott hotel remains under investigation by Pakistani authorities.
Pakistani security officials say it was caused by an electrical short circuit and insist they have found no indication of terrorist activity or a bomb blast.
But some hotel guests who were there say the blast, which tore through the hotel lobby, was powerful and sudden, indicating it was from a bomb.
The State Department says a U.S. embassy staffer sustained light injuries in the blast. At least two Italians also were slightly wounded.