LONDON (Reuters) - Tanzania detained and questioned two senior local Acacia Mining staff at an airport this week in a dispute with the government, two sources said on Friday, and the company said it was having trouble renewing work permits for foreign staff.

Chief Executive Brad Gordon denied a Reuters report that foreign staff were asked to leave by the government due to a dispute over mining licenses and accusations of tax evasion.

He said its local employees had been interviewed by Tanzanian “government agencies” but did not confirm detentions.

“We were having difficulty getting work permits renewed. But no foreign nationals have been asked to leave the country. So there may be some confusion in that. That’s a normal part of business,” Gordon told Reuters.

Acacia Mining said this month it was seeking an adjudicator to resolve its dispute over mining contracts after President John Magufuli ordered the suspension of any new licenses.

Tanzania passed two laws this month forcing companies to re-negotiate their contracts as Magufuli pushes through reforms he says will distribute revenue to his people.

The government accused Acacia of tax evasion in 2016 in a case that is ongoing. This year, it accused Acacia of operating illegally. The miner denies the allegations.

“Acacia is fully cooperating with these investigations and has provided extensive documentation and information to the investigating authorities,” Gordon said.

“In addition, employees in Tanzania have been and continue to be interviewed by government agencies as part of the process,” the chief executive said.

Two sources with direct knowledge of the matter said two senior local staff of the mining firm, Tanzania’s largest foreign investor, were detained and interrogated at an airport this week.

Acacia Mining shares were down 7.4 percent by 0852 GMT (4:52 a.m. ET). The company, majority owned by Barrick Gold, reported first half results on Friday showing gold production was up 4 percent year-on-year.