The power tool manufacturing company Milwaukee Tool is facing questions from lawmakers in the U.S. over the organization's reported use of Chinese prison labor within its supply chain, according to The Wall Street Journal.

An investigative study found that Milwaukee Tool has been sourcing work gloves from political prisoners that are forced to work against their will, wrote Senator Jeff Merkley (D-OR) and Representative Chris Smith (R-NJ) in a July 10 letter to Steve Richman, president of Milwaukee Tool Group.

“The issue of forced labor in China, and the unfair trade advantage it offers companies like yours, is one that has plagued the U.S. economy for decades,” Sen. Merkley and Rep. Smith wrote in the letter that was made public July 11. “We understand that Milwaukee Tool may have strongly worded policies against the use of forced labor, as do most every company with global supply chains, but the evidence, in this case, is very compelling.”

Milwaukee Tool allegedly conducted business with a supplier that sources products from the Chishan Prison in the Hunan province of China. Prisoners at the facility are forced to meet certain production quotas, otherwise, they could be subject to punishment, according to Shi Minglei, whose husband — human rights activist Cheng Yuan — is being held at the prison. Shi added that prisoners have said they have produced gloves with Milwaukee Tool’s logo.

“Milwaukee Tool regularly conducts a complete and thorough review of our global operations and supply chain,” a company spokesperson said. “We have found no evidence to support the claims being made.”