CRATER LAKE, Ore. — A married couple camping at Crater Lake National Park were found dead in their tent this weekend, and carbon monoxide poisoning is the suspected cause, the authorities said.

The bodies of Tory Christensen, 27, and Aleathia Christensen, 25, of The Dalles, were found by a Mazama Campground employee Saturday afternoon, said Dave Brennan, chief ranger at the park.

A cause of death has not been determined, but the couple's tent was tightly closed and a propane camping lantern had been burning inside, Brennan said.

There were no signs of violence, and the ranger said it did not appear that the couple committed suicide.

Brennan said the couple had likely been dead for a couple of days. Autopsies are to be performed this week and the investigation remains active.

"It's tragic," Brennan said. "You're not supposed to die when you are out recreating and vacationing."

Brennan said he was told that Aleathia Christensen worked as a nurse in The Dalles and Tory Christensen was a construction worker.

Roughly 30 deaths and 450 injuries are attributed each year to carbon monoxide poisoning from the use of portable camping heaters, lanterns, or stoves inside tents, campers and other vehicles, according to the U.S. Consumer Product Safety Commission web site.

The symptoms of carbon monoxide poisoning include headache, dizziness, weakness, nausea, vomiting, sleepiness, and confusion. Carbon monoxide reduces the blood's ability to carry oxygen. Low blood oxygen levels can result in loss of consciousness and death.