KARACHI, Pakistan -- U.S. and Pakistani investigators searched the site of a deadly car bombing outside the American Consulate in Karachi on Saturday, trying to piece together clues about the attackers.
A previously unknown group claimed responsibility for the massive blast Friday that killed 10 people and injured 45. The bomb blew a gaping hole in the heavily guarded consulate's perimeter wall, shattered windows in buildings a block away and sent debris a half-mile.
The devastation made it hard to piece together events leading up to the bombing, even which vehicle contained the explosives. It also caused confusion over the death toll: Officials put it at 11 on Friday but lowered it to 10 on Saturday, citing difficulty sorting out body parts.
Initial reports indicated a suicide attacker was responsible, but police said they also were looking at the possibility that the bomb was hidden in a car carrying the head of a driving school and three female students, then set off by remote control as it passed the consulate. Police said they believed those in the car were unwitting victims in the attack.
"We are keeping all options open ... this could be one possibility which can't be ruled out," said Brig. Mukhtar Shaekh, home secretary in Sindh province.
A U.S. Consulate spokesman, who declined to be identified, said American teams, including FBI investigators, were coming to Karachi to investigate the crime scene and evaluate structural damage to the building. Additional security also was arriving.
"We are looking for information that will be useful in identifying the perpetrators and finding evidence that would bring the criminals to justice," the spokesman said.
The United States promptly closed its consulates in Karachi, Lahore and Peshawar, as well as the American Center in Islamabad. A State Department official said a decision will be made soon whether to reopen them on Monday.
"This explosion is a stark reminder again to all Americans living in and traveling through Pakistan of the need to pay attention to their personal security situation," the U.S. Embassy in Islamabad said in a warning issued to Americans in Pakistan.
Security was tightened at the U.S. Embassy in Kabul, in neighboring Afghanistan.
The attack -- the fourth against foreigners in Pakistan since January -- also prompted the U.S. government to consider scaling back its diplomatic staff in Pakistan, which has become the front line in the war against al-Qaida.
No Americans were among the dead, but a U.S. Marine guard and five Pakistani employees at the consulate had slight injuries.
U.S. officials in Washington said they suspect al-Qaida or affiliated Islamic extremist groups carried out the attack.