Monmouth County First Assistant Prosector Robert Honecker said all five people inside the building had been rescued, with four taken out within an hour of the blast and the last person pulled out about 2 p.m.
The victims, all in critical condition, were taken to local hospitals with crushing injuries, Honecker said. Their identities had not been released as of Friday afternoon.
Most were found in the basement of the building, though Honecker was not sure whether they had been in the basement before the blast or ended up there. The explosion, shortly before 11:30 a.m., caused the first floor of the one-story store to pancake down into the basement.
Four of the injured were store employees, and the fifth worked for Kiley Construction of Long Branch, the company that was doing the electrical work blamed for the explosion.
''A third of the roof has collapsed, there's debris all over, the glass is all blown out. This was a tremendous explosion,'' said Harry Conover, director of emergency management for Monmouth County.
The last person rescued was a young woman who used her cell phone to call for help.
Honecker said all store employees were accounted for, but dogs were being brought in to make sure no customers or other people were still trapped inside. He said the local gas company had turned off the gas line that blew and had crews on site. A search-and-rescue team from Fort Dix Army base also responded to the emergency, and nearby streets were closed to traffic.
A construction worker had alerted store staff to the broken gas line. Employees evacuated customers and were in the process of evacuating animals when the explosion occurred, said Shawn M. Underwood, spokesman for San Diego-based Petco Animal Supplies Inc.
Store employee Alison Hazelet, 20, of Brick Township, said she was grooming a shih tzu named Cuddles and started feeling nauseated right before the explosion.
''The general manager came by and said, 'Get out!''' said Hazelet, who grabbed the dog and ran outside.
Cuddles, who was not injured, was being held in a van belonging to the Monmouth County Society for the Prevention of Cruelty to Animals a few blocks away, said the shelter's director, Ursula Goetz.
The shelter had staff and vans waiting in a parking lot across the street from the store to remove animals from the destroyed building once authorities gave them the go-ahead. Three local veterinary hospitals offered to help treat any injured animals, and those unhurt would be cared for at the SPCA, Goetz said.
She said Cuddles' owner, June Mahon of Holmdel, came to the shelter Friday afternoon looking for the dog and was redirected to the staff caring for him.
''She was just panicky. She figured her dog was dead,'' Goetz said. ''She's overjoyed'' the dog is OK.
The store normally has fish and small animals --birds, guinea pigs, ferrets, gerbils, mice and lizards-- and recently opened a grooming facility for larger animals, Goetz said. It was unclear how many animals were inside at the time of the blast and whether any besides Cuddles were rescued.
The center of the roof appeared to have collapsed, with wires and insulation hanging in the air, but part of the 10,000-square-foot building's facade was still intact.
Petco operates more than 700 stores in 47 states and the District of Colombia.
