Big Island Civil Defense kept Highway 19 closed yesterday afternoon after dangerous levels of naphtha were found in the air following a fuel spill.

Earlier in the day, an 8,000-gallon fuel truck overturned in the Kaawalii Gulch area.

"Because of the spill, it soaked into the soil, and when they did the measurements, they measured vapor in the air," said John Drummond, Civil Defense administrative officer.

Naphtha, a colorless, flammable liquid that is used as a raw material for gasoline, fuels the 63-megawatt power plant owned by Hamakua Energy Partners, which supplies energy to the Big Island, Kusch said.

A private contractor removed the soil and replaced it with other fill, authorities said.

The road was reopened at 3:45 p.m. after a fire hazardous-materials team determined the gases were unreadable and deemed the area safe, said fire Battalion Chief Matthias Kusch.

Kusch said the vapors did not sicken anyone since the area is remote and no homes are in the area.

The truck, owned by C&F Trucking, was fully loaded and carrying fuel from Hilo to the Hamakua power generation plant in Honokaa when the accident occurred after 6:15 a.m. on the Honokaa side of the gulch.

The fuel tank ruptured, and most of the naphtha fuel leaked out, the Fire Department said. A vacuum tanker was able to remove a portion of the fuel, and the tanker was righted and towed away.

The driver was injured and taken in serious condition to a hospital in Hilo, Big Island police said, but the extent of his injuries was not reported.

Highway 19 was cleared by 2 p.m., but traffic was not allowed because air quality was at unsafe levels for public access. The highway closure cut off traffic between Honokaa and Hilo, forcing drivers to travel around the island or across the Saddle Road to get to their destinations.