Toxic gases add to hazards near Hawaii's erupting Kilauea volcano

PAHOA, Hawaii, May 15 (Reuters) - Toxic gas emanating from steaming gashes on the flank of Hawaii's erupting Kilauea volcano on Tuesday added to the danger facing residents, whose escape routes are threatened with closure because of lava flows, officials said.

Dangerous levels of sulfur dioxide gas and other emissions prompted state health officials to urge residents to stay indoors or leave the eastern end of Hawaii's Big Island, which has been ravaged by volcanic activity since May 3.

A 20th fissure releasing lava and gases has opened on Kilauea's side, state officials said on Tuesday.

Lava oozing out of fissures have hit the island's lower Puna area especially hard, tearing through farmland some 25 miles east of the volcano's smoking summit, destroying 37 homes and other structures and posing a risk of blocking one of the last exit routes, state Highway 132.

No deaths or major injuries have been reported, but officials have ordered about 2,000 residents to evacuate the area.

Near-constant small earthquakes and gas emissions have not driven all area residents away.

Mark Clawson, a 64-year-old semi-retired plumber, said he was not ready to leave his spacious Upper Kapoho hilltop home, where he has lived for 15 years.

"It's a lot more fun today than it was yesterday," he said Monday. "Yesterday it was just too unnerving."

Lava from one of the fissures has been moving toward a coastal dirt road that is also a key access route for some 2,000 residents in the southeastern area of the Big Island, home to around 200,000 people.

Mass evacuations would be triggered if either highway is hit by lava, Hawaii National Guard spokesman Major Jeff Hickman said.

President Donald Trump on Friday approved a disaster declaration that makes federal relief available to the state.

The Federal Emergency Management Agency, which has a team in place on the Big Island, said it would assist the state with at least 75 percent of emergency measures and replacing damaged infrastructure.

The U.S. Geological Survey has warned that pent-up steam could cause a violent explosion at the volcano crater, launching a 20,000-foot plume that could spread debris over 12 miles.

Scientists had expected such explosions by the middle of this month as Kilauea's lava lake fell below the water table. But water may not be entering the crater, as feared, and gas and steam may be safely venting, scientists said.

(Reporting by Terray Sylvester in Pahoa and Jolyn Rosa in Honolulu, additional reporting by Andrew Hay in Taos, New Mexico; Writing by Peter Szekely in New York; editing by Scott Malone and Jonathan Oatis)