Three people were killed in the fire, with at least five injured.

Cecilia and Danilo Obien and other family members quietly watched their building burn, as they sat at a nearby Dunkin’ Donuts store.

“Everything is buried, everything is gone,” said a trembling Cecilia Obien, as she talked to relatives on the phone. “We have nothing left.”

The Obiens and other tenants — many of them senior citizens — were in shock as flames consumed the “working class” building.

“They were trembling and upset,” The Star-Ledger reporter Ana Alaya told the Filipino Reporter, referring to the Obien family. “They were all in shock and didn’t know what to do.”

The explosion occurred at 9:36 a.m. and hundreds of firefighters responded, as smoke could be seen miles away.

Shortly before the explosion, a Montclair contracting crew preparing to remove an underground oil tank reported hearing a “popping sound that signaled a gas pipe may have been compromised,” according to a statement from the company, American Tank Services.

Firefighters and a crew from Public Service Electric & Gas were summoned to the scene, but Bergenfield Fire Chief John Pampaloni said he saw no evidence of a gas leak, although residents nearby reported the odor of gas.

Police and utility company officials said a preliminary investigation showed that a hole dug by construction workers collapsed and pinched a gas line that fed the building just before 9 a.m.

The workers were attempting to remove and replace a 2,000-gallon oil tank.

Investigators are still trying to determine what ignited the explosion.

Filipino-American businessman and civic leader Buddy Deauna said St. John Roman Catholic Church opened its doors to house some of the evacuees, and the school district offered temporary rooms and showers.

He also said the American Red Cross is also helping the displaced residents.