OTTAWA - The mystery of the missing mint gold is deepening.

The Royal Canadian Mint announced Tuesday that the RCMP has found no evidence of theft in the apparent disappearance of $15.3 million in gold and silver.

The Mounties sent a letter stating that their probe into the "unreconciled differences" in 2008 inventories provided no evidence to support further criminal investigation.

"A thorough investigation was conducted of all investigative leads which could have conceivably supported criminal wrongdoing," Supt. Stan Burke wrote.

"The RCMP would like to inform the mint that our inquiries and investigation to date do not support further effort in the continuance of a criminal investigation into this matter."

The conclusion is consistent with security and computer-system reviews conducted at the mint's Ottawa facility by the Banks Group and Microsoft Services, the mint said in a statement.

Last June, a review by the accounting firm Deloitte and Touche concluded that accounting errors were not to blame for discrepancies between the value of the precious metals on the mint's books and the stockpile on hand.

So what happened to the gold?

The mystery could be cleared up in mid-December, when the mint plans to release its own reports once the auditor general finishes reviewing its 2008 financial statements.

The mint's chairman, James Love, said last spring that a computer programming glitch could explain the missing stockpiles.

Nevertheless, the mint notified its insurers it intended to file a claim to offset the amount of any unreconciled differences.

The government announced in June that it had instructed the mint's board to withhold all executive bonuses "until this matter is resolved to our satisfaction."

It also imposed a requirement for the mint to report on inventory levels of precious metals every three months.