Two key House Republicans have given a skeptical appraisal of the Energy Department's efforts to clean up its Paducah, Ky., uranium plant, publicly questioning the agency's assurances that workers and neighbors are safe.

Despite an official finding last month of "no imminent hazards" at Paducah, the department's own reports show significant radioactive contamination outside the plant in areas accessible to the public, Reps. Thomas J. Bliley Jr. (Va.) and Fred Upton (Mich.) wrote in an Oct. 12 letter to the White House.

In one ditch near the plant, radiation levels were high enough to prompt inspectors to return to the site in protective suits, the lawmakers noted, citing testimony by Energy Department officials.

"Clearly there is a serious threat of radiological contamination to anyone who may access these uncontrolled areas," said the letter, released yesterday.

Bliley, chairman of the House Commerce Committee, and Upton, chairman of the panel's oversight and investigation subcommittee, are leading one of two congressional probes into environmental and safety problems at the 47-year-old Paducah Gaseous Diffusion Plant, which once supplied enriched uranium for nuclear bombs.

Republicans in recent weeks have criticized the department for failing to recognize the problems years before they became public in August. In the Oct. 12 letter, Bliley and Upton also accused the department of impeding progress by refusing to share results of environmental monitoring at the plant.

"DOE has not demonstrated that it is capable or fully committed to ensuring the safety of the community surrounding the Paducah site," they wrote.

Administration officials dismissed the charges as baseless, citing what they described as an aggressive response by Energy Secretary Bill Richardson to reports of past worker exposure to radioactive plutonium at Paducah. Besides the probe launched by Richardson in August, he also ordered a 24-hour safety "stand-down" at the plant and issued an apology and a promise of compensation to ailing workers.

A preliminary investigation last month found "no imminent hazards" that would warrant an immediate shutdown. But the probe did uncover "serious problems," including lapses in safety practices and radioactive contamination off site.

Administration officials fired back at the Republican-controlled Congress for failing to fund programs to speed up medical monitoring at Paducah. Of $21.8 million in increased funding requested by Richardson, lawmakers approved $10 million for accelerated cleanup but no additional money for workers. "We are serious about keeping our commitment to the workers, so we'll find the money," said David Michaels, assistant energy secretary for environment, safety and health.

After the expected release of a final report on Paducah next week, plant officials will have 30 days to come up with a detailed plan for fixing safety problems.

A second Paducah investigation, which looks at worker exposures before 1990, entered a new phase this week with Energy Department interviews with more than 150 employees who worked at the plant before 1990. Carolyn Huntoon, assistant energy secretary for environment management, met with some of the workers yesterday during a tour of the plant.

Investigators are already sifting through hundreds of records and other evidence submitted by workers and by neighbors of the plant. One 1998 memo suggests that managers knew of at least one area outside the plant where radiation could pose a risk.

"Even though this section is rather small, . . . the potential exists for the unescorted general public to have access to an area with the potential for a high dose of radiation," the memo states. In a 1991 document, a state police investigator cites allegations from confidential sources of illegal dumping of radioactive waste outside the plant. The now-retired investigator, Don W. Senf, of the state's Hazardous Devices Unit, told commanders in a report that the alleged dumping had gone on for years. Senf, in an interview last week, said his commanders did not investigate the claims.

A Kentucky state police spokesman said yesterday that the agency did act by checking radiation levels at a police firing range near the plant. "We didn't find anything there," Lt. Kevin Payne said.

CAPTION: Spreading Toxins (This graphic was not available)