A business partner of the owner of the 22-foot-fishing vessel Nikki B. said yesterday the two men most seriously injured in the explosion of the vessel Saturday at Wai'anae Boat Harbor are recovering. One of them underwent surgery yesterday at The Queen's Medical Center, he said.

An investigation into the cause of the explosion is ongoing.

Witnesses who saw the boat explode early Saturday morning said the blast shook the ground and blew people off their feet.

Calvin Nunies, who described himself as a relative and administrative partner of Nikki B. owner Dencio Biliboa, said yesterday he suspects an ethanol-related gas leak could have caused the explosion by compromising the boat's fuel line.

"Alcohol went eat 'em up," Nunies said of the boat's fuel line.

Ethanol or alcohol fuel is an alternative to gasoline and can be blended with gasoline to reduce consumption of fossil-based petroleum fuels.

The Nikki B., recently rebuilt, was headed out for a fishing excursion at 6:30 a.m. with a party of four when the explosion occurred.

Two of three men aboard the boat who were thrown into the air were seriously injured.

Biliboa, 35, landed on the pier after the explosion and complained of not being able to feel anything in his legs. He underwent surgery yesterday at The Queen's Medical Center, Nunies said.

"He broke his tailbone and is in (the Intensive Care Unit)," Nunies said. "We have to see how the surgery goes. We can put the business on hold. We want (Biliboa) to get back healthy first."

Romeo Gayacan, 52, is also at Queen's with a broken leg and may have to undergo reconstructive surgery, Nunies said.

The third man, whom Nunies did not know, and a teenage boy, who was on the pier helping the boat cast off, escaped serious injury.

They were treated Saturday at the Wai'anae Coast Comprehensive Heath Center and released, Nunies said.

"They took the boat out three weeks ago and no trouble," Nunies said.

The state Department of Land and Natural Resources is investigating the cause of the explosion. Harbor Master William Aila could not be reached yesterday for comment.

Reach Rod Ohira at rohira@honoluluadvertiser.com.