COPENHAGEN, Denmark — Seven Danish mayors say restaurants will be closed across northern Denmark and people in the region will be encouraged to be tested after authorities found a mutation in the virus in 12 residents who got infected by minks.

At the same time, the borders to seven northern Denmark municipalities will be closed, the mayor of Vesthimmerland, told Danish broadcaster TV2. Birgit Hansen, the mayor of the port town of Frederikshavn, said only people with “critical functions” can cross municipal boundaries.

People in that region, which has numerous mink farms, also will be urged to work from home.

The restrictions, which are to be announced later Thursday, would begin Friday and last for four weeks.

The move comes after Denmark’s Prime Minister Mette Frederiksen said Wednesday that all 15 million minks in Danish farms should be culled to minimize the risk of them re-transmitting the coronavirus to humans.