The New York City police commissioner James O" Neill too called the subway pipe-bombing a "terror-related incident'.
"At this point in time, all we know of is one individual who, thank God, was unsuccessful in his aims", Mayor de Blasio said.
He had a homemade device that either did not fully detonate or malfunctioned in some way, resulting in burns to his hands and abdomen as well as lacerations.
Port Authority police moved quickly and strategically, arresting Ullah at gunpoint on the spot.More news: Rahane's father detained by police
Police confirmed one person was in custody but were not yet identifying the device used.
As he was taken into custody, Ullah made statements to cops after waiving his Miranda rights, federal authorities noted. "But we will give you more information, of course, as the investigation unfolds", de Blasio said.
Law enforcement searched Ullah's home in Brooklyn Monday.
Four people were injured Monday in the blast that rocked a subway station in the heart of Manhattan, firefighters said, but none of those injuries was life-threatening.
Early media reports said the blast came from a pipe bomb, and that several people were injured.
Veronica Chavez was with her son Alex after being treated for ringing in her ears. Service will resume. Let's go back to work. "We can't be scared". The normally busy area was empty after police evacuated the area.More news: More than a kettle and bell
- Alan Butrico owns a residential building next door to the building where he says Ullah and his family live.
While there is no evidence that Ullah had any contact with ISIS or other extremist groups, he told investigators he had been inspired by the group's online propaganda, a senior official told NBC. "That is exactly what they want and that is exactly what they're not going to get".
NY governor Andrew Cuomo said the bomb used was an "effectively low-tech" device. "I just thought, not another situation again".
Mr Cuomo said: "This is NY".
"This attack underscores the need for Congress to work with the president on immigration reforms that enhance our national security and public safety", she told reporters in an afternoon news briefing.More news: Tillerson says U.S. won't set preconditions for North Korea talks