KARACHI, Pakistan — U.S. federal agents joined Pakistani police Saturday as the investigation into a bombing outside the American Consulate here in Pakistan's largest city intensified and the death toll from the attack rose to 11.
The upward revision of those who died in Friday's explosion came when police recovered parts of an additional body, apparently of a female victim. She was believed to have been riding in a driver education car that was blown apart by the blast.
Fifty-one people were injured, including six inside the consulate compound who were hit by flying debris.
Although both U.S. and Pakistani officials stressed that the investigation was in its preliminary phase, they acknowledged that evidence gathered during the initial 24 hours had heightened the possibility that the blast might not have been the work of a suicide bomber but was instead detonated by someone from a safe distance.
"We're not ruling out a suicide bomb, but we're focusing on the possibility of a remote control device," said Mukhtar Ahmed, who as home secretary for Sindh province has overall responsibility for law enforcement in Karachi.
Ahmed and senior police officials involved in the case said that preliminary questioning of relatives and friends cast doubt on the likelihood that any of those killed was a suicide bomber.
Police said none appeared either to have had contacts with militant extremist groups or to fit the profile of such an attacker.
The female driving instructor and three young women traveling in one of the two vehicles suspected of carrying the explosives were on their way back to school from a local motor vehicles department office, where the three students had just attained their driver's licenses. All the occupants of the car were killed.
The second vehicle under suspicion, a small Suzuki commercial van, carried a man and his niece who were on their way to pick up money and jewelry from a bank safe deposit box in advance of the young woman's planned marriage Saturday. Both were killed, and the remains of the van ended up as an unrecognizable twisted piece of metal crammed by the force of the explosion into small gazebo-like structure in a park across the street from the consulate.
Fayaz Leghari, the deputy inspector general of police charged with leading the investigation, said Pakistani forensic experts were seeking assistance from recently arrived FBI teams to determine which of the two vehicles carried the bomb.
"We've asked the FBI for help in this regard, and they've promised to have an answer for us tomorrow or the day after," he said.
The Toyota sedan belonging to the driving school had been recently serviced at a local garage, and the mechanic was questioned Saturday by police and then released, Leghari said.
He added that investigators had not ruled out the possibility that the bomb-carrying vehicle had been hijacked before being driven to the consulate.
Another development under investigation by police was the bizarre behavior of a young man, apparently Pakistani, outside the consulate a few minutes before the blast. A prominent local journalist, Kamran Khan, who was at the consulate's main entrance minutes before the bomb detonated, said he was approached by a young man with a mobile telephone and some papers who asked hurriedly, first, if the large building was the American Embassy and then, whether the offices were on the right or left side.
Khan said he believed at the time that the young man was acting strangely.
Leghari said police had yet to determine the veracity of a note faxed to several local newspapers late Friday by a group calling itself Al Qanoon, or the Law, that claimed responsibility for the attack. The note also denounced the United States and its ally Pakistan and declared that the attack was merely the first volley in a holy war that the group has declared against the two countries.
To some extent, the note added to the confusion surrounding the case.
"We're taking it seriously," Leghari said. "But this is the first time we've had a note claiming responsibility for such an attack, so we're not certain what to make of it."