SANDY BEACH — A brushfire scorched about 50 acres along the Ka Iwi coast near the Makapu'u lighthouse yesterday afternoon, prompting the closure of the highway for 6 1/2 hours because of thick smoke.

No homes were threatened, but several hikers on the lighthouse trail were temporarily stranded, and smoke could be seen from as far away as Niu Valley.

Officials closed Kalaniana'ole Highway at 3:30 p.m. between Sea Life Park and Kealahou Street because of poor visibility, said fire department spokesman Capt. Kenison Tejada. Officials would open the road for brief stretches periodically whenever the smoke thinned out.

The Fire Department's Air One helicopter dropped bucketloads of water onto the fire, which was brought under control about 8 p.m. The highway was reopened about 10 p.m.

Firefighters did not immediately know what started the fire.

Motorists heading to Windward O'ahu were detoured at Kealahou Street and had to take the Pali Highway or one of the other trans-Ko'olau routes. But a chemical spill near Castle Medical Center backed up Pali traffic all the way to Waokanaka Street in Nu'uanu for several hours.

Honolulu fire officials said the department has fought more than 576 brushfires so far this year, compared with 569 for all of 2004.