The Chief Executive of BHP Billiton didn't hide his frustration concerning the "tea money" graft scandal in Cambodia.

Marius Kloppers recently sent a statement to all the employees to remind them on following work ethics for the company to achieve success.

From his memo obtained by BusinessDay, he said that the probe will continue forensically. However, it is still at a "relatively early stage."

''You should be assured that we will thoroughly and fairly investigate these matters, as we would any other possible breach of law or the code, and take whatever action is appropriate at the conclusion,'' the CEO said.

Also on the memo, Kloppers reminded the staff to be consistent with the company's code and charter values.

''That means working in a way that upholds our values, which underpin everything we do. We also know that consistent and proper business conduct creates loyalty and trust."

The memo was released after BHP revealed it has been probed by the US Securities and Exchange Commission since last year. During the investigation, it discovered evidences on possible corruptions linking with government officials.

Media reports speculate the bribery scandal amounted up to $US1 million as payment to the Cambodia government in 2006 to obtain bauxite leases.

BHP's internal investigation also discovered that Cambodia's non-tax revenue from mining concessions for 2006 was only $US443,886, which raised a question on where the money was spent.

The miner has continuously battled issues on fraud and bribery and facilitation payments for more than five years.

Analysts claimed that a US probe in the alleged bribe could impair BHP's reputation and threaten its chances of acquiring an approval from its iron ore merger with miner Rio Tinto.