Zambia temporarily shut its border with Tanzania to enhance measures against the spread of the new coronavirus, delaying its main copper exports via Dar es Salaam, a minister said on Tuesday.

President Edgar Lungu on Sunday directed the closure after the border town of Nakonde recorded 76 cases of COVID-19, the respiratory disease caused by the virus, the highest number registered by Africa’s No.2 copper producer in a single day.

South Africa’s strict coronavirus lockdown has caused miners to divert copper from the country’s ports to others in Africa, with Dar es Salaam the clear winner.

“We have a good number of trucks that need to be cleared to go out of Zambia,” Muchinga province Minister Malozo Sichone told Reuters by phone from Nakonde.

Sichone said priority would be given to trucks entering Zambia with essential goods such as fuel, medical supplies and food. He could not say for how long the border would remain closed.

“What will inform us is the extent to which we disinfect the town and test people,” Sichone said.

The number of new coronavirus cases in Zambia rose to 267 on Sunday and deaths to seven, Health Minister Chitalu Chilufya said.

Tanzania has confirmed 509 cases of the coronavirus, with 21 deaths, according to the World Health Organization. However, the government has been criticised for not providing regular updates on the spread of the outbreak, and the opposition has accused it of being secretive.