The roof of a pet supply store collapsed Friday after a damaged gas line exploded, injuring five people and killing hundreds of small animals, authorities said.

All five were rescued from the rubble and taken to the hospital. Four were Petco (search) store employees and one was a construction worker who had gone in trying to help people get out, officials said.

The explosion caused more than half of the single-story store to collapse into the basement.

"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.

County prosecutor Robert Honecker said the victims were hospitalized, some in critical condition, with what he described as crushing injuries. Authorities did not release their identities.

The explosion occurred as employees were evacuating customers and animals after construction workers damaged an unmarked gas line outside the store and then smelled gas, said Shawn Underwood, spokesman for San Diego-based Petco Animal Supplies Inc.

One woman was rescued after she used her cell phone to direct rescuers to her, Underwood said.

SPCA (search) investigator Buddy Amato said hundreds of animals, mostly rodents and fish but also 40 geckos and about 70 parrots and parakeets, were in the store when it collapsed. At least 100 had been taken out alive by Friday afternoon.

"We're going to be here all night," Amato said as animal handlers and volunteers carried out live animals, including fish placed in buckets and plastic bags because their tanks were broken.

Three veterinary hospitals offered to help treat injured animals, and those unhurt will be cared for at the SPCA, said Ursula Goetz, director of the Monmouth County Society for the Prevention of Cruelty to Animals.

Petco operates more than 700 stores in 47 states and the District of Columbia.