An explosion occurred Saturday in Seaside Heights, N.J., followed by one in the Chelsea neighborhood in Manhattan. The latter blast left 29 injured. An unexploded pressure-cooker device was also found four blocks away and was being analyzed by the FBI. Here is what we know so far:
On Monday morning:
The NYPD tweeted a picture of Ahmad Khan Rahami, 28, who is being sought in connection with the Chelsea blast. New York mayor Bill de Blasio told CNN's New Day that Rahami, a New Jersey resident of Afghan descent, is a naturalized U.S. citizen.
In addition, the FBI released a wanted poster for Rahami, 28. His last known address is listed in Elizabeth, N.J., and the poster warns that Rahami "should be considered armed and dangerous." Elizabeth is about 15 miles south of lower Manhattan.
"This is someone who was likely involved in one way or another" with the Chelsea bombing, New York Mayor Bill de Blasio told CNN's New Day. "We need to get this guy right away."
Meanwhile, federal authorities were conducting a raid on a New Jersey apartment above a fried chicken restaurant.
Just before 8 a.m. ET, authorities issued a cell phone alert via its Notify NYC system about the search for Rahami. It said, "WANTED: Ahmad Khan Rahami, 28-yr-old male. See media for pic. Call 9-1-1 if seen."
According New York City's official website, NYC.gov, "Notify NYC started as a pilot program in December of 2007 in four areas. It went citywide May 2009 as a means to communicate localized emergency information quickly to city residents.
"The City wanted a way to update New Yorkers quickly with official information after several incidents occurred in 2007, such as: tornadoes, a steam pipe explosion, and crane collapses. Since its inception, Notify NYC has sent out thousands of notifications about local emergencies."
From Sunday and overnight:
A device found in a backpack near a train station in New Jersey exploded early Monday while a bomb squad robot was trying to disarm it, authorities said. Christian Bollwage, the mayor of Elizabeth, said that two men found a bag containing five devices in a trash can at about 8:30 p.m. Sunday. The bag had wires and a pipe protruding from it. Christian Bollwage, the mayor of Elizabeth, said the FBI was attempting to disarm one of the devices when it exploded at around 12:30 a.m. Monday. There were no immediate reports of any injuries or damage.
NJ Transit services were suspended between Newark Liberty Airport and Elizabeth, and Amtrak trains to New Jersey were being held at New York Penn Station. Amtrak trains heading to New York were held in Trenton early Monday. Passengers said they were stuck on trains for hours Sunday night. Amtrak said 2,400 passengers were affected.
Bollwage said the FBI was bringing another robot to remove the four remaining devices found in New Jersey, WUNF News reported. "I don't believe the City of Elizabeth at this stage — was a target," he said, according to WUNF.
New York Mayor Bill de Blasio said Sunday that people will see "a very substantial NYPD presence this week — bigger than ever."
The heightened alert comes as world leaders are gathering Monday for the United Nations General Assembly. President Obama is expected to attend the annual meeting Tuesday, the last of his eight-year tenure.
What happened on Saturday?
The Chelsea explosion occurred just after 8:30 p.m. ET on Saturday at 133 West 23rd St., between Sixth and Seventh Avenues in a neighborhood with a bustling nightlife. The fire department said 29 people were hurt by the blast, but none of the injuries were life-threatening and all those hurt people were released from area hospitals by Sunday morning. The explosion was from an apparent homemade device placed in front of a residence for the blind and near a major thoroughfare with many restaurants. A second device, believed to be a pressure cooker, was later found four blocks away on West 27th Street and was safely removed early Sunday, according to the New York Police Department.
Earlier Saturday in Seaside Heights, N.J., a pipe bomb exploded near a Marine charity run. In that instance the device was placed in a garbage can. No injuries were reported.
Was it a terrorist attack?
New York Gov. Andrew Cuomo said Sunday that investigators so far have not found any connection to international terrorist groups, and that there is no further immediate threat to the city.
New York Mayor Bill De Blasio called the incident an "intentional" act" but said the city had received "no specific and credible threat" from any terror organization.
What evidence is there?
A federal law enforcement official, who was not authorized to comment publicly, told USA TODAY that surveillance footage shows what appears to be the same person moving devices into place at the site of the Chelsea explosion and at the location where the undetonated pressure cooker was discovered.
FBI agents conducted a traffic stop just off the Verrazano bridge, which connects Staten Island to Brooklyn, Sunday night. The agency said the stop was related to its investigation of the Chelsea explosion.
We did a traffic stop of a vehicle of interest in the investigation. No one has been charged with any crime. The investigation is continuing— FBI New York (@NewYorkFBI) September 19, 2016