Pakistan has detained at least four people suspected of having links with Faisal Shahzad, the Pakistani-American arrested in the US over a failed bid to set off a car bomb in New York's Times Square.
"They have been picked up on suspicion that they knew Faisal Shahzad," a Pakistani security official said on Friday.
One of the four arrested was reportedly connected with Hanif Rajput Catering Service, a catering company which the US embassy accused of having "terrorist" links.
A government official has said one of the detained suspects was the co-owner of the catering company.
The US embassy in Pakistan issued a warning on Friday about the catering company.
"The US Embassy is aware of threat information suggesting that terrorist groups may have established links to the Hanif Rajput Catering Service," the embassy said.
The Times Square bomb plot has revived fears about Pakistan, a US ally, being a breeding ground for violence against US targets.
US prosecutors said Shahzad had admitted to being involved in the failed Times Square bomb attack and has been cooperating with investigators since his arrest on May 3.
Prosecutors said Shahzad, who has a wife and two children in Pakistan, had travelled to a Taliban and al-Qaeda stronghold in Pakistan to receive bomb-making training.