Faisal Shahzad, 30, a naturalized U.S. citizen of Pakistani origin, was arrested Monday at New York's Kennedy airport just prior to the departure of his Emirates flight to Dubai. U.S. investigators now believe he might have had ties to the Pakistani Taliban and that some of them may have trained him.
However, CNN reported a spokesman for the Pakistan Taliban denied any connection to Shahzad.
The report also quoted a senior U.S. official saying that new leads developed in Pakistan show Shahzad likely had training from extremists but would not say if that was tied to the attempted bombing in New York. It was also not clear which group may have been involved with Shahzad.
Shahzad has reportedly told investigators about receiving training in bomb-making in Pakistan's Waziristan tribal region.
The Times of London also reported the Pakistani Taliban's denial of any link to Shahzad. A Taliban spokesman praised him but also said, "We don't even know him."
Since Shahzad's arrest, Pakistani authorities have detained a number of people, including a friend and one of his relatives.
Pakistan's Daily Times reported Thursday three people were detained by police in Lahore, capital of Punjab province. Sources told the newspaper Pakistan's Interior Ministry has directed intelligence agencies to immediately interrogate Shahzad's relatives in Lahore, but it was not clear if those detained are relatives.
The Daily Times, quoting witnesses, also reported some of the relatives in Peshawar, concerned about Shahzad's arrest, have locked their homes and gone underground.
CNN, quoting intelligence officials, reported a team of U.S. and Pakistani investigators questioned Shahzad's father in Peshawar and also interrogated four people linked to the militant group called Jaish-e-Mohammed, which is connected to al-Qaida.
Shahzad is reported to be one of two sons of a retired Pakistani air force officer, but the CNN report said the father was not detained or arrested.
A New York Times report quoted Western diplomats and intelligence officials as saying the Pakistani Taliban are now working with al-Qaida and several other groups to expand their activities even as their capabilities get degraded by Pakistani military operations and escalating U.S. drone strikes.
The report said alliances with other militant and terror groups have helped the Pakistani Taliban continue their activities and even improve their skills.
"They trade bomb makers and people around," a senior U.S. intelligence official told The New York Times. "It's becoming this witches' brew."