A private collection of World War II-era grenades and other munitions exploded in a garage in the German town of Hennef, east of Bonn, on Monday, leading to a large-scale security operation and the arrest of the owner, police said on Tuesday.

Police said authorities were called after an explosion was heard at a home in Hennef. Upon arrival, they found a garage in flames and heard still more explosions.

Fearing further blasts, security authorities cleared a wide area around the home, shutting down a stretch of railway and highway and evacuating several homes.

The grenades were carelessly stored

When explosives experts arrived on the scence, they discovered that a crate of grenades from the Second World War had been stored in the garage and had exploded, apparently owing to the unseasonably high temperatures currently prevailing in Germany.

Read: German authorities seize WWII heavy weapons collection

Weapons offenses

The 51-year-old owner of the munitions, who now faces possible charges of violating weapons laws, said he had purchased them at a flea market. He was taken into temporary detention.

Smoke rose over the town amid the explosions

The remaining munitions were destroyed in a controlled explosion in a field. Police are still investigating the exact circumstances of the incident.

Read: Thousands evacuate Düsseldorf after discovery of WWII bomb

tj/rg (AP, dpa)