The bomb that injured 29 people on Saturday in Manhattan was filled with shrapnel and made with pressure cookers, flip phones and Christmas lights that set off a powerful explosive compound, law enforcement officials told The New York Times Sunday. Another bomb that did not detonate was designed with similar features.

Both bombs appeared designed to create maximum chaos and fatalities — they also provided a trove of clues even as any suspects remained unnervingly at large.

A top law enforcement official said that pressure cookers were filled with “fragmentation materials.” The bomb that exploded, at 23rd Street, was filled with small bearings or metal BBs. A second device on 27th Street that did not explode appeared to be filled with the same material, the official said.

Authorities are focused on the possibility that the attack was connected to a bombing that took place 11 hours earlier in New Jersey. But experts are still comparing the bombs and techniques used to construct them.

Three pipe bombs were tied together, placed in a trash can and also employed by a flip cellphone as a timing mechanism, according to officials. Only one of the three pipe bombs detonated and no one was injured. Officials said the explosive in that device appeared to be black powder.

In addition, CNN reported Sunday night that "key video" had identified possible suspects in the Manhattan bombing.

Investigators on Sunday sifted through blast remnants, examined video and scoured the scene of an explosion that wounded 29 people in Manhattan, attempting to establish if there were any links to international terrorism.

CNN reported Sunday that the bomb that exploded in New York City, along with another secondary device found later, was "similar by design" with a pipe bomb that exploded Saturday in New Jersey. FBI investigators are continuing to examine all of the devices and the bomb debris as well as video of the blast.

The two devices in New York City both used a cell phone as a timing device, CNN reported. The phones were also similar in design, officials said.

Three devices along a charity-race route in New Jersey — only one of which exploded — were also rigged to detonate using a cell phone as a timer.

The devices in New Jersey contained black powder, which is an easily attainable explosive ingredient, several law enforcement officials told CNN. "None of the devices are very sophisticated, but they show enough know-how to be lethal," CNN reported.

The explosion on a commercial and residential street in New York City's Chelsea district on Saturday night sent a deafening roar and a powerful shock wave through several blocks, wounding people with shrapnel and flying glass. All 29 victims were released from the hospital, officials said on Sunday.

Mayor Bill de Blasio pleaded for any witnesses to provide tips and promised a security presence that would be "bigger than ever" for the United Nations General Assembly bringing together world leaders in Manhattan for six days starting on Tuesday.

With so little known about the attack, officials said they would deploy an additional 1,000 state police and National Guard to sensitive areas such as transportation hubs.

Federal Bureau of Investigation investigators will examine remnants of the bomb plus an unexploded device found four blocks away as well as a pipe bomb that exploded about 80 miles (130 km) away in New Jersey on Saturday to see if they were connected, officials said.

Police recovered video from both scenes in Manhattan including images of the explosion itself, New York Police Commissioner James O'Neill said.

New York police, the FBI and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives converged on the site for their first daylight view of the site of the explosion, cordoning it off and placing dozens of evidence markers on the ground. Police closed several surrounding blocks to traffic.

"We are in the middle of a very complex post-blast investigation," O'Neill said.

Although no international group had claimed responsibility, New York state Governor Andrew Cuomo said detonating a bomb in New York City "is obviously an act of terrorism."

But the mayor resisted on Sunday when reporters pressed him to call the blast an act of terrorism, saying investigators had yet to determine if there was a political motivation. There were no obvious political targets on the block.

"It was intentional. It was a violent act. It was a certainly a criminal act. It was a bombing. That's what we know," said de Blasio, flanked by high-ranking officials of the FBI and the city police and fire departments.

"It could have been something personally motivated. We don't know yet," de Blasio said.

The blast happened the same day as a knife attack at a mall in central Minnesota when a man wounded nine people before he was shot to death by an off-duty police officer. The assailant was a "soldier of the Islamic State," the militant group said on Sunday.

In a statement on Sunday, Democratic presidential nominee Hillary Clinton said: "I strongly condemn the apparent terrorist attacks in Minnesota, New Jersey, and New York."

Her Republican opponent, Donald Trump, referring to the Manhattan blast, said on Saturday: "We better get very tough, folks."

The mayor and the governor both promised that New Yorkers would not be cowed and that apart from the street closures, life would continue as normal. New Yorkers who endured the Sept. 11 attacks in 2001 and devastating Superstorm Sandy in 2012 said they were generally unperturbed.

A sweep of the neighborhood following the blast turned up another device four blocks away consisting of a pressure cooker with wires attached to it and connected to a cell phone.

Pressure cooker bombs were used in the 2013 Boston Marathon bombing that killed three people and wounded more than 260.

The New Jersey explosion came from a pipe bomb, officials said. A U.S. official familiar with information circulating inside the government said the motive remained unknown and insufficient evidence had been gathered to link the two New York bombs. There was no evidence to connect them to the New Jersey blast, said the source, who spoke on condition of anonymity.

"Almost anybody could have fabricated these bombs and used cellphones as timed detonators," said another U.S. official familiar with the inquiry. "There are instructions all over the internet, and the crudity, positioning, and relative ineffectiveness of these does not suggest that a more sophisticated group played any role in this."

The FBI would examine all three devices at its special crime laboratory in Quantico, Virginia, Cuomo said, but city officials said the police bomb squad still had possession of the unexploded device as of midday on Sunday.

Unclear what caused #Chelsea blast - Sr #NYC official tells @jonathan4ny PD searching for devices as a precaution pic.twitter.com/oyqFd7hCn4 — Mike Walker (@New_Narrative) September 18, 2016

Videos show scene in Chelsea, where authorities are responding to blast near 23rd and Sixth https://t.co/ZLPbwIXvBF pic.twitter.com/5hxFLmu7TV — New York Daily News (@NYDailyNews) September 18, 2016

25 injuries to civilians confirmed at 133 W 23 St #Chelsea. None appear to be life-threatening at this time — FDNY (@FDNY) September 18, 2016

There's really not a lot to see/hear. Just saying: scale of this seems modest on the scene, not major-international-incident type of thing. — Nate Silver (@NateSilver538) September 18, 2016

A cop tells someone wanting to breach cordon: 'It's a crime scene. People are hurt. There's been an explosion.' #NYC pic.twitter.com/wMVE4MxJYc — Tim Teeman (@TimTeeman) September 18, 2016

At least 15 people reported injured in New York City explosion, FDNY says - WABC, New York Post https://t.co/ptqtuPYQgU — Breaking News (@BreakingNews) September 18, 2016

Officials have not said what caused explosion. https://t.co/eXN13Qn51g — Maggie Haberman (@maggieNYT) September 18, 2016

UPDATE: NYPD confirms "several" people injured in explosion were transported to hospitals https://t.co/H5Etk2t3eg pic.twitter.com/4dlXW9NjTU — The Hill (@thehill) September 18, 2016

NBC NEWS: A senior NYC Official says 15 minor injuries as the result of the explosion at 23rd and 6th avenue. — Tom Winter (@Tom_Winter) September 18, 2016

Lots of police and fire dept. not clear what happened. Reports of explosion in dumpster in chelsea nyc. pic.twitter.com/xxpFCU5qKv — Richard Engel (@RichardEngel) September 18, 2016

.@NYPDnews & EMS on scene of apparent explosion on 23rd & 6th. Monitoring closely. Will provide updates w/ confirmed information. — Bill de Blasio (@BilldeBlasio) September 18, 2016

Details unclear regarding NYC explosion, and active disinformation is circulating, so stay cautious. Something happened, not clear what. — J.M. Berger (@intelwire) September 18, 2016

Donald Trump tells crowd at Colorado Springs rally that a “bomb went off in New York.” Unclear what caused explosion pic.twitter.com/1o0SNklnwR — BuzzFeed News (@BuzzFeedNews) September 18, 2016

UPDATE: President Obama has been told about New York explosion, cause of which is still under investigation: White House official — Reuters Politics (@ReutersPolitics) September 18, 2016