"After smoke formed in two train cars at 6.30 [a.m. local time, 4:30 GMT] the ICE 511 was stopped on the way from Cologne to Munich and evacuated quickly. The high-speed line Koeln-Rhein/Main [between Cologne and Frankfurt] has since been blocked," the railway company said in a statement.
Following the smoke appearance, the fire broke out in two train cars, the train operator said. Fire brigades were summoned to put it out.
Five people were lightly injured in the fire in a high-speed Cologne-Munich train in Germany, Bild newspaper reported.
The fire broke out in a rear train car and spread over to the next car.
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German railway operator Deutsche Bahn said earlier in the day that over 500 passengers of the train were evacuated.
According to the operator, long-distance trains between Cologne and Frankfurt are diverted to the old Rhein route via Mainz and Koblenz, so the travel time will increase by 80 minutes.
Deutsche Bahn added it was unclear how long the suspension would last since the investigation was ongoing.