A family firm linked to Japan's new Foreign Minister Taro Aso is under scrutiny over allegations it used Korean labour during colonial rule.
Mr Aso's family ran the mining company during colonial rule
South Korea asked Japan about more than 100 such firms, an official said.
The list includes Aso Mining, which was owned by relatives of Mr Aso, and is suspected of using thousands of Koreans as forced labourers.
The report comes as relations between Japan and its East Asian neighbours have deteriorated sharply.
Seoul has said it had no plans for a summit with Japan at an upcoming East Asian meeting.
The issue of Aso Mining was raised between the two sides, at a meeting this week to discuss repatriating the remains of Korean conscripted workers, said Choi Bong-tae, from a bi-lateral commission investigating the fate of forced labourers.
But Mr Choi said the Japanese government provided no information on the company.
However a spokesman for the parent company of a successor of Aso Mining, Aso Cement, said it would be difficult to provide such data.
"We couldn't investigate into the history of Aso Mining even if we wanted to, because records just aren't available from so long ago," Akira Fujimoto was quoted as saying by the Associated Press.
"All we can say is that everybody employed forced labour during the war. There must have been a dozen mining companies in Kyushu at the time, and they all used forced labour. So it wasn't a practice limited to Aso Mining," he said.
Taro Aso, who was appointed Japan's foreign minister in a reshuffle in October, has also been under fire in the region this week for comments he made about Yasukuni shrine, which honour's Japan's war dead.
"The only countries in the world that talk about Yasukuni are China and South Korea," Japan's Nihon Keizai newspaper quoted Mr Aso as saying.
South Korea and China are angry that Japanese politicians, including Prime Minister Junichiro Koizumi, choose to repeatedly visit the shrine, despite the fact that it pays homage to 14 people judged as war criminals after World War II.
Mr Aso's South Korean counterpart, Ban Ki-moon, said that although a summit with Japan was unlikely at the upcoming Asean (Associated of South East Asian Nations) meeting, he would nevertheless seek talks with the Japanese minister.
"I'm going to use spontaneous opportunities ... to exchange views with Foreign Minister Aso on his perception of history and to deliver the position of our government," Mr Ban said.
"I'm thinking of telling [Aso] that he, as foreign minister, should take a more cautious attitude and that would be helpful to resolving various pending issues amicably."