NEW YORK (AP) — It's still not clear who was behind an explosion last night in New York City that injured 29 people.

Mayor Bill de Blasio called it an "intentional act" but declined to call it terrorism.

A law enforcement official says the blast that rocked a bustling Chelsea neighborhood appeared to have come from a construction toolbox in front of a building. The official also tells The Associated Press that a second object found four blocks from the blast scene appeared to be a pressure cooker attached to wiring and a cellphone.

The Fire Department said 24 people were taken to hospitals with injuries. One person received a puncture wound that was considered serious. The other injuries were described as scrapes and bruises.

All have now been released from local hospitals.

PIPE BOMB BLAST

SEASIDE PARK, N.J. (AP) — The FBI is taking over the investigation of a pipe bomb blast that occurred in a New Jersey shore town shortly before thousands of runners were due to take part in a charity 5K race to benefit Marines and sailors. The bomb was in a plastic garbage can when it exploded.

The agency won't say whether investigators believe the incident in Seaside Park was terror related.

Two other devices were found that did not explode.

Brad Cohen, the acting special agent in charge of the FBI's office in Newark, has declined to take questions from reporters, citing the "active, ongoing" investigation.

Officials say residents who had been told to leave their homes earlier in the day would be allowed to return Saturday night. But several beaches in the area will remain closed until further notice.

No injuries were reported in the blast.

Officials say runners had been scheduled to pass by the area around the time the blast occurred. But the start of the race had been delayed and no one was in the immediate area when the blast happened.