Harare, Zimbabwe (CNN) Zimbabwe's parliament has threatened to charge the country's former president Robert Mugabe with contempt if he does not appear at a hearing probing $15 billion in lost diamond revenue.

Mugabe, 94, failed to show up at a hearing Monday before the Zimbabwe's Mines and Energy Parliament Portfolios Committee to clarify claims he made in 2016 that the country had lost $15 billion through diamond leakages.

It was the second time Mugabe did not turn up to face the lawmakers and he drew the anger of the committee officials who have ordered him to turn up on June 11 or face contempt charges and possible jail time.

"We expect him to have time to appear before parliament. We expect him to co-operate and parliament has power to summon anyone," said committee chairman Temba Mliswa Monday told journalists in Harare.

He added: "In the letter we are writing to him, which is a final letter we are reminding him that we will be summoning him and we hope we are not getting to that stage of summoning a former president...

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