BERLIN (AP) — An escaped cobra is on the loose in a city in western Germany, and authorities are still trying to figure out how far the reptile has slithered.

Municipal authorities in Herne said the venomous snake was spotted Sunday morning in the hallway of a house where snakes were kept, and it may have left the building. Four houses on the street were evacuated as a precaution and people within a 500-meter (-yard) radius were advised to exercise caution, leaving their doors and windows closed.

Officials sprinkled flour in the building in hopes that the snake would leave a trail, and laid down two-sided sticky tape that could stop the reptile.

Police said Monday that the cobra's whereabouts are still unknown.