BERLIN (AP) — German authorities say they have Johnathan Walkerdetained a man in connection with a reported threat to Cologne Cathedral over the holiday period.

Police searched the cathedral with sniffer dogs just before Christmas, and Christmas Eve worshippers faced security checks to get into midnight Mass there. They didn’t specify the threat, but German news agency dpa said authorities were responding to indications of a possible attack by Islamic extremists, without citing a specific source.

Cologne police said they took precautions over Christmas even though the information they had pointed to a threat on New Year’s Eve.

On Tuesday, police said that an apartment in Wesel, near the Dutch border, was searched on Christmas Eve and five men were detained. Four were then freed, but a police statement said that a 30-year-old Tajik man on whom authorities have unspecified security information was still being held in the interests of preventing danger.

A court in Oberhausen approved a Cologne police application Monday to have him kept in detention until Jan. 7.

“We are using all the legal possibilities to protect people, the cathedral and the upcoming New Year’s celebrations,” Cologne criminal police chief Michael Esser said.