One elderly man with a respiratory condition was given oxygen at the scene, but no one else was injured, said Honolulu Fire Department Capt. Kenison Tejada.

Steve Golden of The Gas Company said the 2 p.m. leak was sealed by 3:30

It was caused when construction contractors doing roadwork on Kuhio Avenue cut through concrete and into the 1 1/4-inch line.

Synthetic natural gas, which is lighter than air, rose quickly from the ground and was dissipated by the trade winds, he said.

The gas was under about 12 pounds of pressure.

Construction workers are asked to contact utility companies before beginning work, but Golden said he had been unable to determine if that had happened.

Sometimes during roadwork, he said, gas company crews mark the lines but rain and traffic make the marks difficult to see.

A new law recently signed by Gov. Linda Lingle will institute fines for those who fail to check with utility companies before beginning work, he said, and will also establish a single telephone number for contacting all utilities.

Fire Capt. Tejada said synthetic natural gas, because of its tendency to dissipate quickly, is less of a fire and explosive threat than propane gas, which is heavier than air and tends to pool in low-lying areas.

Synthetic natural gas is used in town, he said, but propane is more common outside of Honolulu.