"The source of the fire remains unknown, speculations at this point are premature," the spokesperson said.
Earlier, local authorities had released a statement attributing the incident to flying sparks from a passing train. At least 32 people were injured when flames spread from some bushes along the side of the railway tracks to nearby houses in the town of Siegburg.
"It happened very quickly as a consequence of the dry and windy weather," Deutsche Bahn spokesperson said.
More than 500 fire fighters spent the greater part of the night trying to get the fire under control until a morning shower of rain alleviated the situation.
In spite of the use of water guns and a fire department helicopter, the damage to several of the affected dwellings was so extensive by then that they will most likely have to be torn down.
The ICE high-speed train connection between Cologne and Frankfurt reopened on Wednesday with "only slight delays" according to the Deutsche Bahn spokesperson. Regional railway traffic is still heavily-disrupted as a consequence of the fire.