http://www.msnbc.msn.com/id/44155883/ns/travel-news/

"BANGKOK тАФ An investigation into the mysterious deaths of a U.S. woman and four other tourists in hotels in northern Thailand has suggested a link to toxic chemical exposure, but failed to determine exactly what killed them, according to a government website Tuesday.

..The victims тАФ from New Zealand, France, and Britain as well as the U.S. тАФ were staying at three different hotels in the popular northern Thai city of Chiang Mai.

A Thai tour guide also died, and three other tourists fell ill but recovered.

No one has been declared responsible in the spate of deaths, which came in January and February.

"The specific agents that caused the deaths and illnesses in these events cannot be identified, and it can not be determined exactly how people were exposed to them," the Department of Disease Control said on its website Tuesday.

The results were most revealing concerning a 23-year-old New Zealand woman who died Feb. 6, her two females companions тАФ both also 23 тАФ who got sick but recovered, and a 47-year-old Thai woman who died February 3.

The four are "most likely to have the same cause of illness, probably exposure to some toxic chemical, pesticides or gas," the report states.
.The deaths of a British couple in their 70s found in their hotel room Feb. 19 were "possibly related" to the those deaths "as they occurred in the same hotel," the report states.