Laos detained two Americans who dumped $3,000 in the Mekong River to announce a $2.5 million reward for the safe return of missing U.S. servicemen, a Thai women who visited the pair said Tuesday.

Pornthipa Vajarabukka, a hotel public relations official, told United Press International the pair, identified as James Copp and Donna Long, were to be released Wednesday once Laotian officials were satisfied they were not spying.A U.S. official in Bangkok, Thailand, confirmed that two Americans were arrested by Laotian police Monday on the Mekong River but said he could not release their names due to a U.S. law protecting individual privacy.

"It is our understanding that the two Americans are now being held in Sing Samphan village in Champassak province in Laos," U.S. Embassy spokesman Ross Petzing said.