BERLIN (AP) — A tunnel-boring machine apparently caught fire Monday deep inside a railway tunnel being built under the Austrian Alps, prompting 12 workers to take shelter, police said. The whereabouts of another three workers weren't immediately clear.

The machine either caught fire or emitted smoke, and 12 workers are believed to have taken shelter in a safety container inside the tunnel, said Stefan Eder, a spokesman for police in Tyrol province.

He said the incident happened "relatively deep inside" the Brenner tunnel, which aims to link the Austrian city of Innsbruck and central Europe with northern Italy. Police said it could be some time before officials have more information on the situation.

An earlier report put at 18 the number of people who had sought shelter in the safety container.

The Brenner project, the main part of which is a 55-kilometer (34-mile) connection between Innsbruck and Fortezza in northern Italy, is supposed to be completed in the mid-2020s. It will consist of two single-track tunnels as well as a third tunnel that will eventually help with drainage.