Frechen, Germany  - Police were checking a German train Sunday to discover how it caught fire overnight, leading to 90 passengers and police being affected by toxic fumes.

The passengers in the air-conditioned train, which has sealed windows, panicked Saturday evening as their carriage filled with smoke and the doors refused to open.

The Regional Express local train operated by Deutsche Bahn came to a halt in Frechen station on the outskirts of Cologne after the fire developed in one of the brakes, police said.

Four transport police officers used fire extinguishers to quell the flames but were themselves sickened by the chemicals.

Ambulance crews treated about 90 of the 180 passengers. Some 18 occupants, including the police, had inhaled dangerous substances and were taken to hospital. (dpa)