JAKARTA: Indonesian investigators have invited Singapore-based oil traders to meet in the city-state next week as part of a US$12 billion corruption probe into state-owned oil firm PT Pertamina.

The requests from the Indonesian attorney general’s office come after earlier notices, sent over the past month, seeking cooperation in the investigation.

Some Singapore-based traders have been asked to attend meetings from Monday (June 2) onwards, said Harli Siregar, a spokesman for the office, adding there was no confirmation that they would attend.

"What matters is that they’re willing to be questioned,” Siregar said by text message. "If investigators have to go [to Singapore], that’s not a problem.”

There is no suggestion that those called to assist in the wider investigation have been accused of any wrongdoing.

Indonesian newspaper Tempo reported Tuesday that the attorney general had asked a unit of Pertamina to assist in calling in nine individuals in Singapore, citing an unnamed person with direct knowledge of the investigations. The report identified the individuals as employees of large trading companies including BP Plc, Glencore Plc and Vitol SA, among others.

BP and Glencore declined to comment. A Vitol spokesperson said the company works in compliance with all applicable laws and regulations, and "seeks to have an open and transparent relationship with the relevant authorities in the jurisdictions in which it operates.”

Singapore-based traders and companies that have received the requests have sought external legal advice to determine the extent of their obligation to foreign investigators, according to people directly involved in these efforts, who asked not to be identified as they are not authorised to speak publicly.

It is not clear if Indonesia has formally sought Singapore’s help under an existing mutual legal assistance treaty. The Attorney-General’s Chambers in Singapore did not immediately respond to an email seeking comment. - Bloomberg