Crews from the Hawaiian Electric Company worked overnight to clean up an estimated 500 gallons of oil that leaked from an underground pipeline in Pearl City last night.

By late morning today, HECO said it had recovered about 90 percent of the oil, which spilled along a portion of the 8-inch, steel pipeline that runs behind three homes.

Fortunately, HECO said the fuel that leaked — low sulfur fuel oil — quickly hardens as it cools, making it easier to pick up.

The incident was first reported at about 5:40 p.m. Tuesday by a Waiawa Road resident who saw the oil in his backyard. HECO personnel responded immediately, shut down the pipeline which it owns and operates, notified the state Department of Health and contained the spill. HECO also offered to relocate the affected residents.

Crews continue to monitor the odor, said HECO, but there are currently no indications of public health hazards.

The pipeline, built in 2004, carries fuel from Barbers Point to the Waiau Power Plant.