Update: (10:35 a.m. Sunday)
All 29 victims of the New York City bombing have been released from the hospital, New York governor Andrew Cuomo said in a press conference Sunday morning.
The explosion remains under investigation.
An explosion in a crowded New York City neighborhood on Saturday night left at least 29 people with serious but not life-threatening injuries, authorities said.
Is it terrorism?
New York Mayor Bill de Blasio said in a press conference Saturday night that the incident was an intentional act but could not identify what caused the explosion. He stressed that the city is not under a credible and specific threat and says a possible terror link has not been confirmed.
Police Commissioner James O'Neill said that gas explosions have been ruled out.
A bomb exploding in New York City is obviously terrorism, but it's not linked to international terrorism.
Cuomo reiterated there was no link to international terrorism, but called the act itself terrorism.
"As governor of New York, this is my worst nightmare," Cuomo said, adding that 1,000 National Guard troops and New York police were deployed.
Another suspicious incident
A pipe bomb exploded in a New Jersey's Seaside Park Saturday shortly before thousands of runners were due to participate in a charity 5K race to benefit Marines and sailors, authorities said.
No injuries were reported in the blast in around 9:30 a.m. Saturday.
New Jersey governor Chris Christie called that incident "clearly an act of terrorism" Sunday morning in a "Fox News Sunday" interview. There are still no clear leads in that incident, but the NYPD confirmed it was not related to the New York City bombings, according to local CNN affiliate NY1.
Police spokesman J. Peter Donald said the explosion occurred in the busy Chelsea neighborhood.
Security cameras captured the explosion as it happened. See it left of the image in the following video at about the 36-second mark.
The earlier suspicious package at 28th Street and 5th Avenue is clear. The briefcase was garbage.— J. Peter Donald (@JPeterDonald) September 18, 2016
Another device was reported near 28th Street, then deemed unrelated.
Pressure cooker device
Several media sources are reporting that a pressure cooker was found sitting out in the open found several blocks away.
CNN is reporting that the second device found is a pressure cooker with dark wires hanging out wrapped in black tape and a cellphone attached to it.
The White House issued a brief statement saying that President Obama had been briefed on the situation. "The president has been apprised of the explosion in New York City, the cause of which remains under investigation," the statement said.
Trump quick to call it "a bomb"
Moments after an explosion, GOP nominee Donald Trump in Colorado said: "I must tell you that just before I got off the plane, a bomb went off in New York and nobody knows exactly what's going on. But, boy, we are really in a time - we better get very tough, folks."
I would like to express my warmest regards, best wishes and condolences to all of the families and victims of the horrible bombing in NYC.— Donald J. Trump (@realDonaldTrump) September 18, 2016
Trump offered his condolences on Twitter on Sunday morning.
Clinton also called it a "bombing"
Democratic nominee Hillary Clinton took a more measured approach but described the incident as "bombings," referring to both the NYC blast and the pipe bomb that detonated in a Jersey Shore town before a Marine charity run.
"I've been briefed about the bombings in New York and New Jersey," she told media on her campaign plane. She is monitoring the situation, aides said.
An 8-year-old is reportedly among the injured. City councilman Corey Johnson tweeted one patient has moderate injuries and the conditions of two patients are unknown.
The patient count is now 26: 23 patients with minor injuries, and 1 with moderate injuries. Condition of 2 add'l patients currently unknown.— Corey Johnson (@CoreyinNYC) September 18, 2016
We are responding to an explosion at West 23 / 6 Ave. - updates to follow— NYPDCounterterrorism (@NYPDCT) September 18, 2016
NYPD's counterterrorism unit has responded to the explosion.
According to one witness, the explosion blew up a dumpster.
People have tweeted out videos of the area near the explosion.
The explosion came on O'Neill's first full day as police commissioner, CNN reports. He succeeded William Bratton on Friday.
New York City on alert
A number of New York City subway routes have been affected by the incident. Authorities have cordoned off several blocks in the Chelsea neighborhood.
Streets remained closed by 10 a.m. Sunday.
The UN General Assembly is Monday
The United Nations General Assembly is set to begin Monday, and foreign leaders had already arrived in New York City when the explosion hit. The U.N. headquarters is about two miles away from the site of the first explosion on 23rd Street.
President Obama will be in New York City Sunday night for a Democratic National Committee fundraiser and stay overnight for the General Assembly.
The Associated Press contributed to this report.