BHP Billiton yesterday joined Rio Tinto in battling graft allegations, saying it had uncovered evidence of possible corruption by employees on an overseas project.

The Australian understands the conduct, now under investigation by the powerful Securities and Exchange Commission in the US, relates to a bauxite exploration project in Cambodia.

BHP has admitted making a $US2.5 million ($2.7 million) payment to the community near the bauxite project, in the northeastern Cambodian province of Mondulkiri, near the Vietnamese border.

A Cambodian government minister described the payment as "tea money", a local term for unofficial payments to government officials.

BHP has rejected this, saying the money was put into a development fund investing in local social welfare programs. The company said it had paid $US1m in September 2006 to the Cambodia government for bauxite exploration rights.

BHP yesterday declined to reveal where the alleged corruption occurred, stressing only that it was not China.

It would not comment on what the behaviour involved and whether employees had stood down or been fired but it said the activities involved mineral exploration, not marketing its products.

Last month, Rio sacked four workers, including Australian Stern Hu, after they were convicted of bribery and stealing commercial secrets related to deals to sell iron ore to Chinese steel mills.

Yesterday, BHP said the alleged corruption was uncovered after the SEC queried it during an investigation into mineral exploration projects.

According to a report in

The Cambodia Daily

in July 2007, the nation's National Assembly was told BHP had paid $US2.5 million to the government to secure exploration rights to a bauxite deposit in Mondulkiri with Japanese industrial giant Mitsubishi.

The claim was made by the then water minister, who described the payment as "tea money".

The minister's comments informed a report into Cambodian corruption by the non-government organisation Global Witness. The report, Country for Sale, details the claims and BHP's rejection of them.

Read more about the BHP corruption claims at The Australian.