Smoke filled four stations along the U3 line in central Munich at rush hour, after a wooden walkway caught fire between Giselastraße and Münchner Freiheit.
U-Bahn staff called the emergency services at 5.40pm, a spokesman from the Munich fire brigade told The Local.
The blaze was brought under control relatively quickly and no-one was injured, but smoke had already spread down the train tunnels meaning that they were not safe to use.
“Trains running on the line took their passengers to safety,” said the spokesman. “It's not something that happens every day.”
The spokesman would not confirm reports that the fire was caused by flying sparks from a power line.
It took until nearly 9pm for the line to be usable again – the exact stretch shut being between Implerstrasse and Scheidplatz. The U6 between Marienplatz and and Dietlindenstrasse was also shut.