In connection with this, Petra Diamonds confirms that a parcel of diamonds (71 654.45 carats) from the Williamson mine in Tanzania has been blocked from export to Petra Diamonds' marketing office in Antwerp and certain key personnel from Williamson are now being questioned by the authorities.
Tanzania's Finance and Planning Ministry said Williamson Diamonds had declared the diamonds were worth $14.798 million but a fresh government valuation estimated they were worth $29.5 million, Reuters reported.
The minister also gave the order after the Tanzania Revenue Authority (TRA) officials, who were present, said that as per the East Africa Community Customs Management Act 2004, section 210 (G) any consignment that is to be imported or exported but whose value is, knowingly, under declared, will be nationalised.
The mine is 75% owned by Petra Diamonds, with the remaining stake held by the Tanzanian state.
It said the final sum to be paid to the government was dependent on what it received from the sale of the gems in Antwerp, rather than the provisional valuation.
Petra confirms that all operations related to the mine are conducted in a transparent manner and in full compliance with legislation in Tanzania and the Kimberley Process.
However the grounds upon which these actions have been taken have not been formally made known to Petra Diamonds as yet.
A parcel of 71,654.45 carats of diamonds from the Williamson mine in Tanzania has been blocked from being exported to Petra's marketing office in Antwerp.
It added it would provide an update "in due course".
Tanzanian President John Magufuli last week ordered a review of a Petra contract and asked public officials to resign over the outcome of an investigation into the mining sector. 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.
Tanzanian authorities seized a shipment of almost 70 pounds of diamonds worth about $33.7 million at the country's largest airport last week.
Mining accounts for about 4% of the south-east African country's economy.