Pakistani police continue to look for leads into the kidnapping of a U.S. citizen from his residence in the eastern city of Lahore.

Development expert Warren Weinstein was snatched by gunmen early Saturday morning after they overpowered guards and broke into his house.

No one has claimed responsibility for the abduction. Police have questioned the two security guards, but say they have come up with few if any leads. The French news agency quotes investigators describing the abductors as Urdu-speakers wearing Western-style clothes.

Weinstein served as the director in Pakistan of a U.S.-based development consulting company, J.E. Austin Associates. Weinstein, who is in his 60s, had worked in the country for more than five years and was scheduled to end his assignment and return to the United States on Monday.

Pakistani police say the kidnappers convinced Weinstein's guards to open a gate just before dawn by offering to give them food. This type of generosity is common during the month of Ramadan, when people fast during daylight hours.

Kidnappings for ransom are fairly common in Pakistan, although foreigners are not usually targets.

During the past few days the U.S. issued a new travel warning for Americans in Pakistan, with specific cautions about the presence in the country of al-Qaida, Taliban elements and indigenous militant sectarian groups. The State Department strongly urged U.S. citizens to take measures for their safety and security at all times, such as maintaining good “situational awareness,” avoiding crowds and keeping a low profile.

Anti-U.S. sentiments run high in Pakistan. Tensions have increased between Islamabad and Washington, during the last three months in particular, after U.S. commandos killed al-Qaida leader Osama bin Laden on May 2 in a raid on the compound where he was hiding in Abbottabad, Pakistan.