BERLIN (AP) — Train services were halted across a swath of northern Germany on Saturday because of what the national railway operator said was a technical problem with communications.

Operator Deutsche Bahn said that no long-distance or regional trains were running in the northwestern states of Hamburg, Schleswig-Holstein, Lower Saxony and Bremen.

That mean that trains between Berlin and Cologne, and between the capital and Amsterdam, also were canceled, while trains from Denmark weren't crossing the border into Germany.

Deutsche Bahn said the cause was a “failure of the digital train radio system,” but didn't give more details or specify how long the problem would last.