A German weapon collector has been arrested after a crate of World War II grenades exploded his garage, reportedly throwing objects more than 30 feet into the air.

Firefighters arriving at the man’s home in Hennef on Monday found more ammunition going off as they tried to put out the flames, the BBC reported.

The 51-year-old owner, who was not identified, told police that he had bought the grenades at a flea market.

Police were quoted in German media as saying they believe the grenades were triggered by warm temperatures.

No one was hurt in the incident and reports suggest the blast sent objects up to 32 feet in the air, the BBC reported.

The collector is facing possible weapons charges and bomb removal experts were called in to destroy the remaining grenades in a field.

Click for more from the BBC.