HONOLULU - Hawaiian Electric says crews cleaned up about 95 percent of the estimated 500 gallons of oil that leaked from an underground pipeline in Pearl City Tuesday evening.

HECO says it was low sulfur fuel oil, which quickly hardens as it cools.  It has a consistency almost like wax and makes it easier to pick up.

The incident was reported at around 5:40 p.m. Tuesday by a resident on Waiawa Road who saw the oil in his backyard while watering his garden. 

"I  was looking down and it was black and shiny.  The oil was moving slowly like a lava flow." explained Gilbert Peter. 

The pipeline was shut down immediately and the Department of Health was notified.  HECO offered to relocate the affected residents, who declined.

HECO says it will further assess the situation on Thursday.

"They're going to excavate and then they're going to be really just finding the leak and figuring out what they have to do.  The could clamp it, or they might need to dig in and weld." explained Shannon Putnam, a spokesperson for Hawaiian Electric. 

The 8-inch steel pipeline was built in 2004 and carries fuel from Barbers Point to the Waiau Power Plant.  The leak happened along a portion of the pipeline that runs behind three homes.  

HECO says the lines are inspected every two weeks.  The line is located within the State Energy Corridor Pipeline, established in 1972 by the State.  

The area of the leak is the closest a pipeline gets to a home.  

The Department of Health says the property is safe and the air quality is being monitored.