Japan acknowledged that Allied prisoners of war were put to work in a coal mine owned by Prime Minister Taro Aso's family, reversing previous denials after newly found documents provided proof.

The Health and Welfare Ministry said Friday that the wartime documents showed that 300 British, Dutch and Australian prisoners worked at the Aso family mine in Fukuoka, southern Japan, from April 1945 through Japan's surrender four months later. It was the first time the government had acknowledged the use of prisoners at an Aso mine.

Two Australian POWs died at the mine, according to a government official who verified the authenticity of the documents.

The disclosure could deal a further blow to the embattled prime minister, whose approval rating has plunged to about 20 percent in just three months since taking office. Aso has repeatedly come under fire for gaffes and lack of leadership through the global economic crisis.

The acknowledgment of the Aso wartime legacy came in response to questions submitted last month by opposition lawmaker Yukihisa Fujita, along with a copy of the documents, which contained records from the prison camp at the mine. Fujita demanded that the government verify their authenticity and the use of Allied POWs at Aso's family mine — a practice the government has long denied.

Aso has kept mum over the latest embarrassment. Earlier this year, he distanced himself from revelations in other wartime documents that Korean forced laborers were used at his grandfather's mine.

"I was only 5 at the time, and I have no personal memory of that," Aso said at the time. Aso briefly served as president of the family company — now called the Aso Group — before becoming a lawmaker

Health and Welfare Ministry official Katsura Oikawa confirmed Thursday that the 43 pages of documents that Fujita submitted — after they were found in the ministry storage — were genuine. Oikawa told a parliamentary committee that the documents had been overlooked for decades because the government had put little effort into examining wartime records.

Japan has acknowledged it used prisoners for forced labor in mines, shipyards and jungles during World War II.

"Many other mining companies had used such prisoners as laborers, and the latest revelation could trigger a wider probe into Japan's treatment of prisoners during the war," said Hiroshi Kawahara, a political scientist at Tokyo's Waseda University.

Historians say many prisoners were beaten and some were executed and contend that the POW death rate at the Japanese camps was seven times higher than that at Allied camps. Thousands of women across Asia were also forced into sex slavery for Japanese troops.

Katsumi Doi, another health ministry official, said Friday prisoners were not mistreated at the Aso mines.

"There is no evidence showing the POWs being abused at the mine," he said, despite the fact that Oikawa said two of the 197 Australian prisoners at the mine died.

Like hundreds of Japanese companies, the Asos' also used civilians forcibly brought from Korea during Japanese colonial rule of that country.

Some health officials told local media that using POWs for labor was standard practice during the war, according to reports published Friday.

Aso's conservative Liberal Democratic Party, which has ruled for most of the postwar era, has often resisted public release of wartime documents. But the opposition bloc, which now controls the upper house after the sweeping election victory last year, now has more access to such information. Doi said the ministry has now submitted all documentation available.

Fujita, a lawmaker from the main opposition Democratic Party of Japan, accused Aso of avoiding his responsibility and the government of looking the other way. Aso was not present at the upper house committee meeting. Fujita could not be reached for comment late Friday.