The US government is investigating BHP Billiton, the mining company, for possible corrupt practices, the company has confirmed.
Media reports said on Wednesday BHP was being probed for its sponsorship of the 2008 Beijing Olympics.
Australia's Fairfax Media reported that the US Department of Justice and the Australian Federal Police (AFP) were investigating allegations that BHP provided inducements, hospitality and gifts to Chinese and other foreign officials.
The Justice Department told Fairfax, in response to a freedom of information request, it was conducting "law enforcement proceedings" involving BHP, which supplied the materials for gold, silver and bronze medals used in Beijing.
The Department of Justice declined to comment after US office hours on Tuesday.
Australian police confirmed they had been working with foreign counterparts and local regulators on Australian aspects of the US investigation.
"Foreign bribery investigations are inherently complex due to their cross-border nature and often involve co-ordination between law enforcement and regulatory agencies," federal police said in a statement without providing further details.
BHP said it had been cooperating with "relevant authorities", and in response to media queries said it believed it had complied with all applicable laws in regards to its Olympics sponsorship.
"BHP Billiton is fully committed to operating with integrity and the Group's policies specifically prohibit engaging in bribery in all its forms," BHP said in an emailed statement.
The world's biggest mining company has been under investigation for possible corrupt practices since at least 2009, disclosing in 2010 that it had uncovered possible violations of some anti-corruption laws.
BHP said on Wednesday it could not comment on whether that investigation had been expanded or whether the probe referred to on Wednesday was separate.
Fairfax reported that between 2000 and 2008, BHP spent millions of dollars on a major Olympics sponsorship deal and hospitality package which according to a former China staffer involved more than 170 VIPs, including senior government officials and Chinese steel and mineral company CEOs.
Unlike most major consumer-focused sponsors, BHP's involvement at the 2008 Beijing Olympics was targeted mostly at its close circle of Chinese buyers and employees.
"Most sponsorships focus on media buys and advertising. We've done almost none," Maria McCarthy, the head of BHP's Olympic sponsorship team, told Reuters news agency in March 2008.
"Instead, we are focusing on community leveraging, stakeholder leveraging that involves governments and customers, and our staff," she said.
A former BHP employee involved in the Olympics arrangements told Reuters that BHP went out of its way to comply with Australian rules and compiled extensive documentation on its activities.
Fairfax Media said the officials BHP entertained included the head of state-owned Chinese aluminium producer Chinalco and the secretary-general of the China Iron and Steel Association, which coordinates industrial policy for China's steel sector.