SEATTLE - New theories are emerging in the mysterious death of a West Seattle woman who was vacationing in Thailand.

Jill St. Onge, 27, died suddenly while traveling in Thailand's Phi Phi Island - a popular island destination for budget travelers - but so far there has been no official explanation for her death.

Family members say St. Onge - a well-known bartender and artist - fell very ill very quickly on Sunday. Her boyfriend, Ryan Kells, didn't even have a chance to get her to a hospital before she died.

Now Kells says he believes St. Onge may have died of fumes emanating from a nearby water treatment plant, according to a story in an English-language Thai news Web site.

"I found out later that there is a water treatment plant right behind the guesthouse," Kells is quoted as saying in the story posted by the Andaman Times.

"I feel that Jill was poisoned by a chemical from that plant. She spent about five more hours in the room than I did. She was just breathing in the fumes for so long," Kells wrote in a posting on a family blog. "The only reason I did not get deathly ill, is that I kept getting these short breaks from the air in the room."

Kells and St. Onge were wrapping up a three-month tour of Asia at a bungalow on the island. They were getting ready to bring home big news - they had gotten engaged during the trip, when tragedy struck.

St. Onge wasn't the only victim of a mysterious sudden death at the same resort. A second woman, from Norway, also died the next day.

Norwegian media and the Andaman Times, which covers southern Thailand, identified the Norwegian woman as Julie Michelle Bergheim, 22.

Both had been staying at the Laleena guesthouse. A 19-year-old Norwegian woman staying with Bergheim also fell ill with the same symptoms, but survived.

"One of them was vomiting so the guesthouse owners and one of their friends rushed her to the hospital on Phi Phi," said police Capt. Pantanan Santhong. "Another one later had the same symptoms. They died at the hospital. Doctors said it was due to dehydration and shock."

According to St. Onge's family, Kells at first thought that his girlfriend had a case of food sickness, so she laid down to rest.

"When (Kells) returned a couple hours later he found Jill in pretty bad shape," says a posting on the family's blog.

"Jill said she needed to go to the hospital. She was so weak he carried her until he found a cart. Ryan was screaming in the streets for help as she was deteriorating fast. They got help from a great guy named Per. He helped Ryan get Jill to the clinic. Unfortunately by the time she arrived she had stopped breathing. They worked on her for around 45 minutes but to no avail. It happened very fast."

Capt. Santhong said local police are mystified by the whole episode.

"Right now, we do not have any further information on what happened and how it happened," he said. "We are investigating."

A number of other theories about what may have caused her death, in addition to the possibility of fumes from the water treatment plant. They include poisoning from food or alcohol and energy drinks, tainted water, cyanide poisoning from an unknown source, or carbon monoxide poisoning.

The cyanide theory was mentioned in an article by a Norwegian newspaper, which reported that traces of the deadly chemical were found in Bergheim's body.

But the Andaman Times reports that police officials have denied any finding of cyanide.

"There are no traces of cyanide. ... This may be a misunderstanding by the Norwegian newspaper," a police source in Krabi told the Andaman Times.

But the Norwegian newpaper, Nettavisen, says it is standing behind its report that cyanide was found, based on reports it received from Thailand.

Asan Buntam, the guest house owner, told the Associated Press that he had nothing to do with the women's deaths.

"I'm sorry about the lady tourists, but it is not my fault," he said. "It was the same thing, their stomachs hurt and they were throwing up. ... I think it was because everyone went out drinking and partying."

Back in the Northwest, bloggers are speculating about the mystery brewing more than 7,000 miles away. St. Onge was a well-known member of the community as an artist and an employee of the Shadowland Restaurant.

"It all seems very suspicious," said St. Onge's best friend Brooke Freed, who received the news on Sunday. "She was just so much a part of our lives. It's impossible to think what its going to be like without her."

Wrangling for answers in an uncooperative foreign land, Kells and St. Onge's family members are determined to get momentum behind the story of her death.

Thai authorities won't allow Kells to bring St. Onge's body home for an independent autopsy, and instead are planning to cremate her body.

"No one knows what happened," said brother Robert St. Onge.

An autopsy was performed overseas, but it was not clear how long it would take to get the results. Estimates ranged from two weeks to several months. The St. Onge family requested blood and tissue samples in order to conduct an independent analysis.