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MAINZ, Germany — A grenade was thrown over a fence and into the grounds of a refugee reception center in southwest Germany early Friday, police said.

The scene of the grenade attack in Villingen, Germany. MARC EICH / EPA

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.

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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.