Fire officials tonight are looking into what caused heavy smoke to billow out of a Hawaiian Electric Co. substation on Kapi'olani Boulevard.

The smoke set off alarms at HECO's Kamoku substation at the corner of Kapi'olani and Date Street about 9 p.m. Firefighters at the scene discovered thick smoke, but saw no flames.

At about 10 p.m., fire spokesman Capt. Terry Seelig said there was no indication as to what was causing the smoke. He said it didn't appear as though the structure was in danger.

HECO spokesman Darren Pai said power was transferred to other circuits and there were on reports of outages. Once fire fighters cleared the building, HECO officials would assess the damage and begin their investigation, he said.