Pakistan?s president, Prime minister and other Cabinet members were supposed to have been at the Marriott Hotel in Islamabad when a massive truck bomb detonated outside, killing 57 and injuring 266, Pakistan?s Interior Minister Rehman Malik said yesterday. Malik said their planned dinner was changed at the last minute, although did not say how far in advance it had been planned.

The Speaker of the House, Fahmida Mirza, had planned the event for ministers, the president, their guests and various foreign dignitaries. But at the last minute, President Asif Ali Zardari asked that the event be transferred to the Prime Minister?s compound, Malik told reporters during a handover service for Czech Ambassador Ivo Zdarek, who died in the blast.

On the day before, Malik called the massive blast ?the biggest attack, volume-wise? in Pakistan in seven years, based on the quantity ? 600kg ? and type of explosives used.Two American military personnel who worked for the US Embassy in Islamabad were among those killed, the US military said. A Lithuanian Pakistan was also among the fatalities, police superintendent Sheikh Zubair told CNN on the day before. The injured included 11 foreigners, Malik said.

No arrests have been made in connection with the attack. But Malik said suspicion is falling on militants in Pakistan?s tribal regions.?I am not in a position to tell you who has done it, but (in) all the previous investigations, all the roads have gone to South Waziristan,? he said on Sunday.

South Waziristan is one of seven agencies of Pakistan?s tribal areas where Taliban and al Qaeda militants are active. But Amir Mohammad, an aide to leader of the Pakistani Taliban Baitullah Mehsud, said he shared the country?s grief and was not involved, The Associated Press reported. Saturday?s massive blast left a nearly 60-foot-wide (18 meters) crater, which was 24 feet (7m) deep, Malik said. It also caused a natural gas leak that set the top floor of the five-story, 258-room hotel on fire, police said. The blaze quickly engulfed the entire structure.

The blast occurred about 7:50 p.m., after the breaking of the fast during the holy month of Ramadan, Malik said. Trees were felled by the explosion, which occurred hours after newly elected President Asif Ali Zardari addressed a joint session of Parliament and promised to root out terrorism. At a news conference in Islamabad on the day before, Pakistani authorities released security video of the blast, showing a small explosion inside the truck before the larger, deadly explosion. In the video, a large truck crashes into the security gate, sending one security officer scurrying for safety. Then, as security guards approach the truck, the top of the vehicle explodes and the security guards flee. Watch guards scatter after an explosion.