ROCKLAND – The cleanup of 4,592 gallons of spilled home heating fuel at Maritime Energy progressed Friday and was expected to continue through spring.

The bulk of the spill, which occurred early Thursday morning and was believed to have been caused by human error, had been removed by Friday afternoon, according to Glen Wall, a spokesman for the state Department of Environmental Protection.

DEP officials said that a couple of people would be working on the recovery effort over the weekend.

Clean Harbors of Portland had been at the site all day Friday, as well as Thursday, Wall said, and would return on Monday to continue sucking up the spill.

At the site Friday, Wall and Peter Blanchard, an oil and hazardous materials specialist for DEP, said that it was difficult to estimate how much of the oil had been recovered because of ice.

The storage tanks that held the oil are close to a creek, which is a tributary of the Weskeag River.

On Thursday, the fuel traveled about 250 yards down the drainage way and had not spread further on Friday, they said.

Because of pockets of oil that get trapped in some spots, the area of the spill would need to be checked until spring when the ground thaws, Blanchard said, and after any heavy rains.

“At some point next week, Clean Harbors will be done,” Wall said.

“I think they made a good recovery,” Blanchard added.

Maritime Energy officials believe that either one of its delivery drivers or a driver from one of the oil companies that buys from Maritime had a problem shifting oil from the pumping station late Wednesday and wedged a block in the valve to keep it open while they checked the system. Apparently, the driver then forgot about the block.

At about 3:30 a.m. Thursday, a truck loaded the pair of 15,000-gallon storage tanks next to the pump station with 9,200 gallons of fuel, not knowing the valve was open.

At around 6 a.m., a company employee smelled the fuel when she arrived at work and noticed the oil spewing from a tank.

Maritime Energy is insured, but company President John Ware did not know Friday whether the spill would be covered. He did not have an estimate on the cost of the cleanup.