BERLIN (AP) — Two Kosovo-born brothers have been detained on suspicion they were planning to carry out an attack on a shopping mall in western Germany, days after a truck attack in Berlin that killed 12 people.

Police said Friday that the men, aged 28 and 31, were detained in Duisburg in the industrial Ruhr region shortly after midnight.

Authorities suspect the two men may have been planning an attack on the Centro mall in nearby Oberhausen. They are now probing what the pair's intentions were and whether anyone else was involved.

Police said in a statement that they increased their presence at Centro and a nearby Christmas market on Thursday evening after receiving a tip from "security sources."

Officers in uniform and plain clothes patrolled the area, but the mall remained open.

Centro is one of Germany's biggest malls, with more than 250 shops. It opened 20 years ago on the site of a former steelworks.

There was no indication of any connection between the detentions and Monday's attack in Berlin.

Authorities are searching for Anis Amri, a 24-year-old Tunisian, as the suspected driver of the truck that plowed into a Christmas market.