Two German archaeologists were kidnapped in central Nigeria on Wednesday, a police official said, near the road that will run between the capital Abuja and its temporary airport from next month.

Abuja’s main airport will be closed for repairs for six weeks from March 8, with flight rerouted to the city of Kaduna some 100 miles (160 km) to the north.

That set-up has raised security concerns. Abuja-bound passengers will have to fly to Kaduna and travel in buses, guarded by security, on a road where several kidnappings have taken place in the past few years.

Kidnappings for ransom are a common problem in parts of Nigeria.

The two German archaeologists were kidnapped on Wednesday morning during excavation work at Jajela village, Kaduna state police spokesman Aliyu Usman told Reuters. It is roughly 19 miles (30 km) from the Abuja-Kaduna road.

“The case was reported by locals and we have swung into action to rescue them,” he said, adding that so far there had been no ransom demand or contact from the kidnappers.

“Unfortunately the victims did not go to the site with the policemen attached to them for security,” he added.

A German foreign ministry spokesman declined to comment.

Nigeria’s government had hoped international carriers would use Kaduna during the main airport closure, but many have said they will not fly there as an alternative.

Some embassies in Abuja also intend to minimize staff travel while the airport is being repaired. Last July, Sierra Leone’s deputy high commissioner was kidnapped on the road.

Its international airport handled 12 flights in December 2015, the last month for which Nigeria’s airports authority has figures, compared with 812 that used Abuja International. REUTERS