A gas explosion at Hawaii Duck Tours’ Kakaako headquarters sent a male employee to the hospital in serious condition with burns yesterday.

The fire had already been put out by employees who reported using an extinguisher by the time firefighters arrived at the Kawaiahao Street location shortly after the 9 a.m. incident, said Honolulu Fire Department spokesman Terry Seelig.

The fire appeared to have been some kind of "flash fire," Seelig said.

Duck Tours is known for its use of distinctive, yellow amphibious vehicles that operate both on land and sea.

Firefighters were called back to the scene about 2 p.m. due to complaints of a strong gasoline odor, but the owner took precautions to ventilate the facility, Seelig said.