Around 200 hay bales caught fire on a field in Bornheim-Merten. Firefighting efforts continued into the evening and could extend until morning.
Responders had to separate the bales because embers remained inside. This made the work considerably more difficult, a fire department spokesperson said.
The field borders a wooded area. Due to ongoing dryness, there was a risk of the fire spreading to the forest. Authorities warned residents via the NINA app to keep windows and doors closed.
The cause of the fire remains unclear. Police have opened an investigation. Hay bales can self-ignite under certain conditions if they were too moist when pressed.