Authorities say 31 eastern European construction workers were injured in a blaze at their apartment in northwestern Germany in a suspected case of arson.

A witness called the fire department in Bergkamen, northeast of Dortmund, early Friday morning to report a burning car in front of an apartment building. When firefighters arrived, they found several tires also on fire in the hallway of the building.

Town mayor Roland Schaefer told the dpa news agency that 33 people from Romania and eight from Moldova lived in the building and worked for a local construction company, though not all were at home.

Dortmund prosecutor Felix Giesenregen said there's no indication yet of any motive.

He says the investigation is looking "in all directions."

Seven of the people's injuries are considered life-threatening.