11 September, 2017
Operations at Williamson have temporarily been stopped for safety and security reasons, Petra said.
Petra has also suspended operations at one of its mines in Tanzania.
Tanzania has been cracking down on the mining industry with a set of new rules that require the government to own at least a 16% stake in mining projects, give them the power tear up and renegotiate contracts for natural resources, and remove the right to global arbitration.
The company was planning to ship them to its offices in Antwerp - the center of the global diamond trade. "The Williamson Diamonds company documents put the value of the diamonds at $14.7m (before cutting and polishing) while their real value is $29.5m", the finance ministry said in a statement.
The government said at the weekend it planned to nationalise the diamonds.
It said the provisional valuation of diamonds from the Williamson mine was carried out by a government agency.
Key personnel from Williamson, which is 75% owned by Petra and 25% owned by the Tanzania government, are being questioned by authorities.
Shares in the company, which said it had not been made "formally aware" of the reason for the investigation, fell almost 25% when the market opened, before recovering to settle around 6% lower, down 6.2p at 83.75p. "The company will provide an update on this matter in due course", said Petra.
Two Tanzanian ministers resigned last week after Magufuli told government officials suspected of wrongdoing in an investigation into the nation's diamond- and Tanzanite-mining industries to step down. Magufuli has also locked horns with foreign mining companies which according to a parliamentary report have underreported their production, thus depriving Tanzania of tens of billions of dollars in revenue since 1998. Earlier in the summer, it was hit with a tax bill for $190bn after government-appointed committees said it was operating illegally and had understated its gold exports.
Francis Massawe, the Manyara regional police commander, said the three officials were arrested in Arusha on Thursday evening, hours after the president was presented with the report and they were later escorted under heavy police guard to Babati, the headquarters of Manyara region.
The president's actions are a continuation of a crackdown in a mining sector that accounts for about 4 percent of Tanzania's gross domestic product.
