A team of the US Federal Bureau of Investigation (FBI) is in Islamabad to exchange information on the New York Times Square bombing plot, Pakistani officials said on Saturday.
A three-member FBI team arrived in Pakistan's capital Friday to obtain information from local officials about their probe into possible links between Islamist extremists and Faisal Shahzad, a 30-year-old US citizen from Pakistan charged in the botched bombing.
"The FBI officials are focusing on two things. First, they want to question Faisal Shahzad's father, father-in-law and his friends so they can guess how that man was radicalized and whether he had any links with radicals," said a Pakistani security official.
"Secondly, they want to know if any militant organisation in Pakistan had sent money to Faisal Shahzad to fund the bombing plot," he said, requesting anonymity. "They want us to find out if any transactions took place through hawala."
The hawala is an informal, private system of quick money transfer that millions of Pakistanis living abroad use to send remittances to the families back home.
US officials say Shahzad has admitted to the plot and told investigators that he attended militant training camps in Pakistan, but authorities in both countries have not confirmed any conclusive contact between him and a terrorist organization.
"We have taken into custody a couple of Faisal Shahzad's friends and people who knew them but there has not been any major breakthrough in the investigation so far," the official said.
"We do not know if this person had any direct or indirect links with Taliban, Al Qaeda or any other terrorist group."
Other officials have said at least one of Shahzad's friends is believed to have links with Jaish-e-Mohammad, a militant group with suspected ties with Al Qaeda and accused of some crimes in Pakistan.
Police arrested the person earlier this week in southern port city of Karachi.
Some media reports said authorities had taken Shahzad's father, Baharul Haq, a retired air vice marshal, into "protective custody" but officially it has not been confirmed.
Shahzad was arrested Monday on a Dubai-bound plane at John F Kennedy International Airport in New York, two days after a vendor spotted smoke arising from a vehicle in Times Square. Police defused the crude car bomb consisting of gasoline, propane and powder.
His links to Pakistani terrorists remain unclear but the pressure is building on the country to act decisively to eliminate Taliban safe havens involved in the insurgency in Afghanistan and Al Qaeda terrorist organization conducting terrorist actions overseas.
US Secretary of State Hillary Rodham Clinton warned Pakistan of "very severe consequences" if a terrorist action on US soil were linked to Pakistan.
"We've made it very clear that if, heaven forbid, an attack like this that we can trace back to Pakistan were to have been successful, there would be very severe consequences," Clinton told CBS in an interview to be aired Sunday.
But Clinton also praised Pakistan's increased cooperation, adding that more was needed from the Islamic country.
"We've gotten more cooperation and it's been a real sea change in the commitment we've seen from the Pakistan government. We want more. We expect more," said Clinton, according to excerpts released by CBS.
Around 150,000 Pakistani troops are carrying out several offensives against Islamist rebels in its lawless tribal region and adjoining Khyber-Pakhtunkhwa province, formerly known as North West Frontier Province.
But they have mainly focused on the militants who have attacked civilian and official targets inside Pakistan, and spared those groups of rebels who conduct cross border raids into Afghanistan.
Large areas of its territory are still under control of so-called "good Taliban" or "Afghan Taliban" who are said to allow Al Qaeda to operate almost freely.