Residents of Hamburg, Germany have been alerted to a toxic smoke cloud drifting towards the center of the northern German port city due to a large fire on Sunday morning that could “affect the air we breathe,” according to local officials.

“The population in the Hamburg area can be affected by smoke gases and chemical components in the breathing air due to a fire,” read an official warning from the Hamburg fire department, which described the alert level as “extremely dangerous” saying “the cloud of smoke is moving towards the city center.”

According to reports from local media, a major fire engulfed “several warehouses” in the Rothenburgsort district of the Hamburg Center in a blaze understood to have begun at around 4.30am local time on Sunday. Numerous explosions were heard, and images on social media have shown plumes of smoke billowing into the air.