BERLIN (AP) — A problem with a communications system forced Germany’s railway system to halt all trains late Tuesday, leaving passengers stranded across the country.

The main national railway operator, Deutsche Bahn, said all trains were being held at stations because of a nationwide problem with the GSM-R digital communication system, which is used for internal communication on the railway network.

Deutsche Bahn said in a statement at midnight, 1 1/2 hours after it first announced the problem, that the cause had been identified, but didn’t specify what it was. It said that technicians “are working intensively on a solution.”

It didn’t specify how long that might take or say how many trains or passengers were affected.

The Bild newspaper quoted Deutsche Bahn CEO Evelyn Palla as saying that “we are now trying to get the trains into stations so that travelers can disembark.”

The company said it would give taxi and hotel vouchers to passengers and, where possible, make available trains at stations for travelers to sit in. It apologized for the situation.

GSM-R, short for Global System for Mobile Communications–Railway, offers voice and data services needed to operate railways, including communication between train drivers and control centers.

According to the European Union Agency for Railways, it has been introduced across Europe since 2000 as a common standard for railway operations.

The German railway system has on rare occasions in the past halted all or most trains, but because of storms rather than for technical reasons.