FTSE 250 miner Bumi said its former Chief Executive had resigned from his current role as non-executive director following the launch of a probe into 'irregularities' at its Indoneisan business.

The firm said Ari Hudaya, who was CEO until March and is also president director of PT Bumi Resources, the focus of the investigation, had resigned from the board with immediate effect.

The "urgent" probe into PT Bumi Resources, in which the company has a 29% interest, is focusing on the firm's development funds.

It relates to a $637m writedown of development funds and exploration assets in Bumi's December 31st, 2011, year-end report.

Bumi said the funds had been marked down to zero in the accounts, except for one investment with a carrying value of $39m.

The company said it intends to contact relevant authorities in the UK and Indonesia in respect of some of the allegations.

The company, whose London listing was driven by financier Nat Rothschild, had already seen shares hit the skids over the last month due to debt worries at Bumi Resources, as well as the falling value of coal.

Commenting on the news analysts at Nomura had this to say: "In the short term, the market is also likely to focus on credit concerns at 29% associate PT Bumi.

Loans from PT Bumi to ReCapital of approximately $340m have yet to be repaid, adding to the group's balance sheet issues. PT Bumi had circa $4.1bn in gross debt and $230m in gross cash at the end of the first half of 2012. We estimate that PT Bumi needs an average Newcastle thermal coal price of over $ 95/tone (versus spot of approximately $87/tonne) to cover its estimated 2013 interest expense."

As well, points out Nomura. "Concerns have resurfaced around the Bakrie's (24% shareholder in Bumi plc) $440m Credit Suisse debt facility. PT Bakrie's entire shareholding in Bumi plc is pledged against the loan. This has led to concern in the market that failure to repay or top up the facility could create additional uncertainty for the group."

At 0900 on Tuesday the company was trading at half the value of a week before.

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