O'Neil said that that the joint task force of city and federal officials was carrying out a "thorough background investigation" of Ullah who lived in Brooklyn.
Four officers are being hailed as heroes for stopping the suspect of Monday's explosion at a New York City transit hub before it got worse.
Officials say 27-year-old Akayed Ullah set off a pipe bomb strapped to his chest Monday morning in an underground walkway connecting subway stations at the Port Authority Bus Terminal.
Relatives and police said Ullah last visited Bangladesh in September to see his wife and newborn son.
It happened just five weeks after another ISIS-inspired terror attack on Halloween on Manhattan's West Side that left eight people dead and a dozen injured. He is believed to have acted alone.
Ullah had no criminal record in Bangladesh, Hoque said, and several United States officials familiar with the investigation told Reuters there was no information indicating Ullah was previously known to USA spy or law enforcement agencies for any connection to militant groups.
New York Mayor Bill de Blasio's office says that he has been briefed about the incident, adding, "The NYPD, FDNY and first responders are on the scene". "Thank God the terrorist did not accomplish his goal".
His wife gave birth to their son in Bangladesh in June and Ullah returned home to visit them in September before coming back the US the following month, according to Mohammed Saiful Islam, a Bangladeshi counterterrorism deputy police commissioner. It consisted of a pipe measuring about a foot long and filled with shrapnel and powder and was detonated by a Christmas ornamental light, a source said. This official said the police charges would likely be dropped when federal charges are filed.
John Miller, the head of police counter-terrorism, said that the device was a pipe bomb attached to Ullah's body with velcro. No charges had been filed as of Monday night.
Earlier, New York Police Department said that it has taken one male suspect into the custody and is responding to the explosion at the 42nd Avenue in the city.
Everything around Times Square was shut down, halting what would ordinarily be a bustling rush hour at the "Crossroads of the World".