American officials are helping Pakistani authorities piece together clues from Friday's car-bomb attack outside the American consulate in Karachi that killed 11 people and wounded 50 others.
Authorities say a high-level team of investigators is working on some leads to find out who was behind the latest attack on foreigners in Pakistan, but they have yet to make arrests in connection with the suspected suicide bombing.
A team of foreign experts, including FBI agents visited the site of the bombing on Saturday. They took photographs and inspected wreckage of some of the damaged cars still lying on the spot.
The powerful explosion destroyed a guard post and damaged part of a security wall that surrounds the U.S. mission in central Karachi. It also shattered windows of hotels in the area.
No Americans were killed, but one U.S. Marine guard and five local employees at the consulate were slightly injured. A previously unknown group called al-Qanoon, "the Law", has claimed responsibility. In a statement, it said "America, its allies and its puppet Pakistani rulers should be prepared for more attacks."
Pakistan is a key ally of the United States in its war against al Qaida-led terrorist groups. A government crackdown on religious extremism is also under way in Pakistan. This policy has outraged many Islamic groups.
Since the start of the year, 15 foreign nationals, including French and American, have been killed in Pakistan.
The United States has condemned the latest attack and has closed its diplomatic missions across Pakistan until further orders. Officials in Islamabad say U.S. Secretary of State Colin Powell has discussed the investigation with Pakistani President Pervez Musharraf. Speaking by telephone, Mr. Powell pledged continued U.S. assistance in fighting terrorism in Pakistan.