Agents with the FBI pulled over a car on a highway in Brooklyn on Sunday night and were questioning the vehicle’s occupants in connection with the investigation into the New York City bombing that injured 29 people, authorities said.

Agents stopped “a vehicle of interest in the investigation” at 8:45 p.m. Sunday, according to FBI spokeswoman Kelly Langmesser.

She wouldn’t provide further details, but a government official and a law enforcement official who were briefed on the investigation said five people in the car were being questioned at an FBI building in lower Manhattan.

The officials spoke on condition of anonymity because they were not authorized to speak about the ongoing investigation.

No one has been charged with any crime and the investigation is continuing, Langmesser said.

The bomb that rocked a bustling Manhattan neighborhood contained residue of an explosive often used for target practice that can be picked up in many sporting goods stores, a federal law enforcement official said Sunday, as authorities tried to unravel who planted the device and why.

The discovery of Tannerite in materials recovered from the Saturday night explosion may be important as authorities probe whether the blast was connected to an unexploded pressure-cooker device found by state troopers just blocks away, as well as a pipe bomb blast in a New Jersey shore town earlier in the day.

Gov. Andrew Cuomo, touring the site of the blast in Manhattan’s Chelsea neighborhood, known for its vibrant arts scene and large gay community, said there didn’t appear to be any link to international terrorism. He said the second device appeared “similar in design” to the first, but did not provide details.

“We’re going to be very careful and patient to get to the full truth here,” Mayor Bill de Blasio said Sunday. “We have more work to do to be able to say what kind of motivation was behind this. Was it a political motivation? A personal motivation? What was it? We do not know that yet.”

Cell phones were discovered at the site of both bombings, but no Tannerite residue was identified in the New Jersey bomb remnants, in which a black powder was detected, said the official, who spoke to The Associated Press on condition of anonymity because the official was not authorized to comment on an ongoing investigation.

Authorities said the Manhattan bombing and the blast 11 hours earlier at the site of a 5K race to benefit Marines and sailors in Seaside Park, New Jersey, didn’t appear to be connected, though they weren’t ruling anything out. The New Jersey race was cancelled and no one was injured.

Officials haven’t revealed any details about the makeup of the pressure-cooker device, except to say it had wires and a cellphone attached to it.

Technicians in Quantico, Virginia, were examining evidence from the Manhattan bombing, described by witnesses as a deafening blast that shattered storefront windows and injured bystanders with shrapnel in the mostly residential neighborhood on the city’s west side. All 29 of the injured people were released from the hospital by Sunday afternoon.

On Sunday, a team of five FBI agents searched an Uber driver’s vehicle that had been damaged in the Manhattan blast, ripping off the door panels inside as they examined it for evidence.

The driver, MD Alam, of Brooklyn, had just picked up three passengers and was driving along 23rd Street when the explosion occurred, shattering the car’s windows and leaving gaping holes in the rear passenger-side door.

“It was so loud,” the 32-year-old Alam said. “I was so scared. There was a loud boom and then smoke and I just drove away.”

Alam said he hit the gas and tried to take his passengers to their destination in Queens, but pulled over along Madison Avenue and 39th Street. He went to a local police precinct to file a report for his insurance company and police contacted the FBI.

The explosion left many rattled in a city that had marked the 15th anniversary of the 9/11 terrorist attacks only a week earlier and where a United Nations meeting to address the refugee crisis in Syria was scheduled on Monday.

“People didn’t know what was going on, and that’s what was scary,” said Anthony Zayas, an actor who was in the Chelsea neighborhood Saturday night when the bomb went off. “You didn’t know if was coming from the subway beneath you, you didn’t know if there were other bombs, you didn’t know where to go.”

Tannerite, which is often used in target practice to mark a shot with a cloud of smoke and small explosion, is legal to purchase and can be found in many sporting goods stores. Experts said a large amount would be required to create a blast like the one Saturday night, as well as an accelerant or other ignitor.

Police and federal spokespeople wouldn’t comment on the presence of explosive material recovered at the scene.

The bomb in Manhattan appeared to have been placed near a large dumpster in front of a building undergoing construction, another law enforcement official, speaking on condition of anonymity to discuss the ongoing investigation, told the AP. The second device, described by the same official as a pressure cooker with wires and a cellphone attached to it, was removed early Sunday by a bomb squad robot and New York City police blew it up in a controlled explosion Sunday evening, authorities said.

Homemade pressure cooker bombs were used in the Boston Marathon attacks in 2013 that killed three people and injured more than 260.

Officials solicited tips from the public, telling reporters at a news conference in the New York Police Department’s headquarters that they didn’t know who set off the bomb or why.

An additional 1,000 state troopers and members of the National Guard were placed at transit hubs and other points throughout New York City and extra police officials were patrolling Manhattan, officials said. Members of the FBI’s Joint Terrorism Task Force were investigating the blast along with New York Police Department detectives, fire marshals and other federal investigators.

Meanwhile, a law enforcement official said federal investigators had discounted a claim of responsibility on the social blogging service Tumblr. Investigators looked into it and didn’t consider it relevant to the case, said the official who spoke on condition of anonymity to discuss an ongoing investigation.

(AP)