The State Department said Monday that Pakistani police are in the midst of a "robust investigation" with the FBI to find abducted U.S. aid worker Warren Weinstein, who was kidnapped form his home in Lahore on Saturday.
By 6 p.m. EST Monday, a senior official told NBC News there still had been no word from Weinstein's kidnappers.
Gunmen snatched development expert Weinstein, 70, before dawn Saturday after tricking his guards and breaking into his house in a brazen raid that heightened fears among aid workers, diplomats and other foreigners already worried about Islamic militancy and anti-U.S. sentiment in Pakistan.
U.S. officials believe the abduction may have been an "inside job," insinuating that the security guards opened the gates of the house for the kidnappers.
"Our priority at the moment is to get this guy back and get him safe," said State Department spokesperson Victoria Nuland in a press briefing.
There are currently no leads as to who is behind the abduction, Nuland said. U.S. officials are concerned that no known groups have come forward and claimed responsibility or demanded ransom.
Weinstein is the country director for J.E. Austin Associates, a development contractor that has received millions of dollars from the aid arm of the U.S. government, according to a profile on LinkedIn, a networking website. He had told his staff that he would be wrapping up his latest project and moving out of Pakistan by Monday, just a couple days after he was kidnapped.
Police were hoping the guards could shed some light on who targeted Weinstein but came up empty-handed, said Shoaib Khurram, a senior police official in Lahore.
"We do not yet have any concrete information that there was a specific threat," Khurram told The Associated Press.
Ransom kidnappings common
Kidnappings for ransom are common in Pakistan, with foreigners being occasional targets. Criminal gangs are suspected in most abductions, but Islamic militants are also believed to use the tactic to raise money.
J.E. Austin Associates stressed Weinstein's commitment to Pakistan's economic development in a written statement and said he has worked with a wide range of Pakistani government agencies, including the Pakistan Furniture Development Company and the Pakistan Dairy Development Company.
"His efforts to help make Pakistani industries more competitive have resulted in many hundreds of well-paying jobs for Pakistani citizens and contributed to raising the standard of living in the communities where these businesses are located," it said.
The company also said Weinstein is in poor health and provided a detailed list of medications, many of them for heart problems, that it implored the kidnappers to provide the elderly development expert.
Shahab Khawaja, a former official at Pakistan's Ministry of Industries and Production, said Weinstein has been working in Pakistan since 2004 and was scheduled to finish his contract with the U.S. Agency for International Development (USAID) on August 15. The two men, who are close friends, met in the capital, Islamabad, in recent days.
"I was shocked and deeply disturbed by his kidnapping," Khawaja said.
Police said Weinstein had returned to his home in Lahore on Friday evening from Islamabad.
Kidnappers tricked Weinstein's guards
According to police, two of the kidnappers showed up at Weinstein's house Saturday and told the guards inside the gate of the walled compound that they wanted to give them food, an act of sharing common during the Muslim holy month of Ramadan.
The guards opened the gate, and five other men suddenly appeared. The armed assailants overpowered the guards and stormed into the house. Some gunmen are believed to have entered through the back. They snatched the American from his bedroom but took nothing else.
According to CBS News, the abduction was carried out by eight men dressed in western clothes. Some of the men may have even been wearing surgical masks to obscure their faces.
Hussain Bhatti, who worked with Weinstein in Pakistan, said the American decided to replace the security company guarding his house in recent months because of general threats to U.S. citizens working in Pakistan. But he did not know who would have targeted Weinstein.
Americans in Pakistan are considered especially at risk because militants oppose Islamabad's alliance with Washington and the war in Afghanistan. The unilateral U.S. raid that killed al-Qaida chief Osama bin Laden on May 2 in northwest Pakistan only added to tensions between the two countries.