NEWPORT — Firefighters, investigators and environmental cleanup personnel spent Thursday picking through the remains of the Friend and Whitney Oil Co. that burned in an intense fire early Wednesday morning.

Although firefighters were called to the Main Street site twice during the night, Assistant Chief Milton Thompson said Thursday morning that the hot spots were extinguished and the rubble was cool enough for investigators to begin digging for answers.

The fire scene was a beehive of activity, with investigators working side by side with cleanup crews. Work to clear the site had begun and removal of the burned out store section was under way.

Downhill from the rubble, two Department of Environmental Protection workers were trying to contain pollutants that continued to flow into the Sebasticook River.

A small eddy next to the oil company was actually pooling the oil and other petroleum-product runoff, said the workers, who were using absorbent pads to remove the oil while it was being contained by booms placed along the riverside.

The workers said that no pollutants were visible downstream.

By late afternoon, Fire Investigator Richard McPeck of the state Fire Marshal’s Office said that some speculation surrounding the fire had been cleared up. Neighbors had told of hearing “squealing tires and breaking glass” at the scene.

McPeck said he believed the breaking glass was from the heat generated within the structure and the squealing tires were from the vehicle of an individual who spotted the fire and did a U-turn in the roadway to report it.

He said that witnesses have reported smelling smoke several hours before the fire erupted, in a similar fashion to the downtown district fire in May, indicating that the breaking glass occurred much later.

“All doors are open, however,” he said late Thursday, adding that nothing, including a human element, had been ruled out as the cause of the fire.

McPeck said that investigators will be on the scene Friday.