A grenade was thrown over a fence and into the grounds of a refugee reception center in southwest Germany early Friday, police said.
No blast occurred, even though the safety pin had been pulled. No injuries were reported.
Police said the device was later destroyed in a controlled explosion.
About 20 residents were forced to evacuate after the grenade was thrown at about 1:15 a.m. (7:15 p.m. Thursday ET) but were able to return to their dormitories a few hours later.
An investigation has begun in to the incident, which took place in Villingen, which is 70 miles south of Stuttgart.
It comes amid a rise in attacks on migrants and refugees as Germany struggles to cope with record influx.
