FBI agents are questioning five suspects over the explosion that injured 29 people in a crowded Manhattan neighbourhood.
The news comes as investigators are also examining a suspicious device found in a rubbish bin near a New Jersey railway station, with the US on high alert.
Here, we look at the investigation so far.
What happened on Saturday night?
The explosion was in the busy Chelsea neighbourhood of Manhattan, on West 23rd street, at around 8.30pm. An unexploded pressure-cooker device was also found four blocks away.
Twenty-nine people were injured and 24 people were taken to hospital. One person received a puncture wound that was considered serious.
Witnesses said the explosion blew out the windows of businesses and scattered debris.
After the incident, Mayor of New York Bill de Blasio ruled out any terror connections but called the blast an "intentional act".
So, what has happened with the investigation into the bomb so far?
The FBI pulled over a car that spokeswoman Kelly Langmesser described as "a vehicle of interest in the investigation" on a road in Brooklyn at 8:45pm local time on Sunday.
Law enforcement sources said five people in the car were being questioned at an FBI building in lower Manhattan.
No-one has been charged with any crime and the investigation is continuing.
And what suspect device has been found in New Jersey?
Late on Sunday evening in New Jersey two men found a package with wires and a pipe coming out of it, Elizabeth Mayor Christian Bollwage said.
He said the Union County bomb squad's robotic device indicated the package could be a live bomb, and the FBI and state police will decide how to remove the device.
New Jersey Transit said service has been suspended between Newark Liberty Airport and Elizabeth. New York's emergency management department said New Jersey-bound Amtrak trains are being held at New York Penn Station.
Wasn't there a bomb in New Jersey, and a stabbing in a Minnesota shopping mall too?
Yes, a pipe bomb exploded in a New Jersey seaside town on Saturday morning shortly before thousands of runners were due to take part in a charity race for US marines and sailors.
No injuries were reported after the blast in Seaside Park, Ocean County but it was the first of a series of incidents that has put the US on edge.
On the same day a man stabbed and wounded eight people at a shopping mall in Minnesota, before being shot dead by an off-duty police officer.
An Islamic State-run news agency claimed the suspect was a "soldier of the Islamic State" who had heeded calls from the extremist group for attacks in countries that are part of a US-led anti-IS coalition.
What happens next?
In New York, detectives are collating video footage from the scene.
And as their investigations continue, the NYPD is urging anyone with information to come forward.
Meanwhile, streets in Manhattan remained closed last night following the blast.