Two warehouses have been on fire in the northern German port city of Hamburg since early Sunday morning.
The fire brigade has warned of the danger from smoke gases and chemical components in the air breathed.
The cloud of smoke is moving from the warehouses in the city's Rothenburgsort district in the direction of the city centre.
The fire brigade could not initially give any information on how exactly the large fire could have occurred during the night or what exactly was in the burning warehouses.
In an official warning, the fire and the growing smoke cloud were classified as "extreme danger."
Residents were being urged to keep windows and doors closed and protect themselves from the smoke in a wide area in Hamburg's north-east.
German rail operator Deutsche Bahn also announced that the tracks between Hamburg and Büchen must be closed due to the fire.
Firefighting efforts are ongoing.
Police in the German city of Hamburg have also warned locals on Sunday of possible toxins in the air after a fire at a storage facility.
Some 140 people have been evacuated, and it is not yet possible to say how dangerous the situation is, a police spokesperson said.
The police spokesperson said the sky had darkened as a result but the weather made it difficult to determine how much was smoke and how much was clouds.
Police and fire authorities were currently assessing the situation, the spokesperson said.
