WASHINGTON - Wisconsin Sens. Herb Kohl and Russ Feingold want the United Nations to send a fact-finding team to Laos to monitor the treatment of Hmong who are emerging from jungles in the southeast Asian nation.

Meanwhile, Rep. Betty McCollum, D-Minn., is urging the Lao government to allow U.S. and U.N. officials to provide humanitarian assistance to the Hmong, an ethnic group from the highlands of Laos.

After decades of fighting the Communist government, often from remote jungles, hundreds of Hmong have been turning themselves in to authorities this year for resettlement. The Hmong population's anti-government stance dates back to the 1960s, when they sided with the United States during the Vietnam War.

U.S. officials have said the Lao government has been granting Hmong fighters an unofficial amnesty as the government resettles them. But outside groups like Amnesty International say there are conflicting reports on whether that is the case.

Feingold and Kohl, both Democrats, asked John Negroponte, the U.S. ambassador to the United Nations, to urge the United Nations to send a fact-finding mission to Laos to ensure that the Hmong are treated humanely.

"Reports indicate that the Laotian government denies the existence of any amnesty program for these individuals," Feingold and Kohl wrote in a letter to Negroponte last week, which their offices released Monday.

"In addition, many of our constituents claim that these former insurgents have been captured by the Lao government and did not surrender."

The letter also was signed by Sen. Mark Dayton, D-Minn., California Sens. Barbara Boxer and Dianne Feinstein, both Democrats, Rep. Mark Green, R-Wis., Rep. Ron Kind, D-Wis., and Reps. George Radanovich and Dana Rohrabacher, both R-Calif.

Sen. Norm Coleman R-Minn., also wrote to the Lao ambassador last week, urging the government to open up areas to human rights groups.

Minnesota and Wisconsin now account for 45 percent of the country's Hmong population, according to census figures. St. Paul Mayor Randy Kelly recently visited a Hmong refugee camp in Thailand.

"We have received the letter and are studying its implications," said Richard Grenell, a spokesman for Negroponte. Officials at the United Nations and the Lao embassy to the United States declined to comment.

T. Kumar, the Asia Advocacy Director for Amnesty International in Washington, applauded the effort to get the United Nations involved.

"The U.N. is the best body at this moment," he said. "We don't know what's happening. That's why it's important that the U.N. take the lead and send a delegation to find out what's happening."

A few months ago, Amnesty International accused the Lao government of using starvation as a weapon against the Hmong, a charge the government denied.

McCollum, meanwhile, who has been championing normalized trade relations with Laos, reached out directly to the Laotian deputy prime minister, Somsavat Lengsavad, urging that humanitarian assistance be granted to the Hmong.

"I am confident that granting international access will also help to dispel the damaging rumors which I have heard this week that the remote people are suffering and being mistreated at the hands of local authorities," she wrote in a letter dated March 13.