The United States believes a blast that wounded several people at the Marriott Hotel in Islamabad was caused by an improvised bomb and not an electrical short circuit as Pakistani officials have said, the State Department said on Friday. "Our information and the information we have shared with the American community is that it was probably an improvised explosive device, a bomb of some kind," spokesman Richard Boucher said.
"But this matter is under investigation by the Pakistani authorities and I'm sure that all our conclusions whether ours or theirs are preliminary," he told reporters.
Pakistani authorities said immediately after Thursday's explosion that it was caused by a short circuit and stuck to that position on Friday despite extreme scepticism expressed by guests and staff at the hotel and US officials.
Earlier, a State Department official told AFP on the condition of anonymity "that the force of the blast and the damage it did is more indicative of an explosive device than something caused by natural means or an electrical malfunction."
Meanwhile, the US embassy in Islamabad warned Americans to stay away from the vicinity of the luxury hotel and a risk analysis unit run by the State Department said a home-made bomb was responsible for the blast that caused extensive damage to the front entrance of the hotel.
The Overseas Security Advisory Council (OSAC), a department-run clearing house for international security information, said in a notice that "an improvised explosive device bombing occurred at the Marriott Hotel in Islamabad, Pakistan."
The brief notice offered no other details about Thursday's blast that shattered virtually every window on the ground floor of the hotel and wounded at least seven people, including three Italian businessmen and a US diplomat who suffered minor cuts from flying glass.
Despite the US comments, Brigadier Javed Cheema, the director general of the Interior Ministry's National Crisis Management Cell told AFP in Islamabad: "We haven't found any evidence that would suggest that it was an act of sabotage."
Another State Department official said the Washington was not convinced by the Pakistani explanation.
"I've seen the pictures and it sure doesn't look like this was an electrical problem," the official said.
Hotel employees and guests reported that the huge explosion could be felt in rooms on higher floors, and the sound of the blast was heard from about a kilometer away.
Aside from extensive damage to the front entrance, the explosion also blew out windows at the back of the main lobby, at least 30 metres from the immediate explosion site, and those in adjoining rooms.