Boston, MASSACHUSETTS (Agencies)

Federal agents arrested two people Thursday in a series of raids across northeastern U.S. states linked to the probe into the failed Times Square bomb attack, officials said.

Authorities are already holding Pakistani-American Faisal Shahzad in custody in connection with the botched bombing, after they hauled him off a plane last week minutes before it was due to take off for Dubai.

"We can confirm that several search warrants have been executed in the northeast in connection with the Times Square bombing investigation," FBI spokeswoman Gail Marcinkiewicz told AFP.

"Two individuals encountered during the searches were taken into federal custody in connection with immigration violations," she added.

The Justice Department and FBI declined to specify where the raids were carried out, but reports in local media named locations in Massachusetts, New York state, New Jersey and Connecticut.

The Pakistani Taliban quickly asserted responsibility for the failed attack, but their claims were initially dismissed by U.S. officials, who suggested Shahzad had acted alone.

Shahzad is alleged to have constructed the crude bomb that was discovered inside a parked car in Times Square on May 1 after a street vendor notified police that smoke was coming from the vehicle.

The discovery forced the evacuation of the popular tourist spot and a massive manhunt that culminated a little more than 48 hours later in Shahzad's arrest as he sat on an Emirates Airlines flight waiting to leave for Dubai.

Shahzad faces five terrorism-related charges and U.S. authorities say he has been cooperating with investigators during interrogations since his arrest.

Taliban's involvement

Last week, U.S. Attorney General Eric Holder said the latest information suggested Taliban was involved.

"We've now developed evidence that shows that the Pakistani Taliban was behind the attack," he said on ABC television's Sunday current affairs talk show "This Week."

Shahzad has allegedly told investigators that he was trained in bomb-making by Islamist militants in the Waziristan region of Pakistan.

The 30-year-old son of a retired Pakistani Air Force officer has not asked for a lawyer and has yet to appear in court after waiving his right to a speedy arraignment.

Justice Department spokesman Dean Boyd emphasized that Thursday's raids were not the related to the discovery of any new threats.

"These searches are the product of evidence that has been gathered in the investigation subsequent to the attempted Times Square bombing and do not relate to any known immediate threat to the public or active plot against the United States," he said in a statement.

Local media reported the locations targeted in Massachusetts included a home in Watertown, and a gas station in Brookline.

The Boston Globe quoted a Watertown resident as saying at least one of the immigration-related arrests was made in the Massachusetts town.

The attempted attack has left residents, visitors and authorities in Times Square jumpy, with several "suspicious packages" that later turned out to be harmless sparking false alarms there in recent weeks.