Unknown thugs have robbed 320 kilograms of gold, 20 kg of silver and one kg of platinum at the Sofia Airport, the Bulgarian Interior Minister Tsvetan Tsvetanov told reporters on Monday evening.

According to Tsvetanov, the bandits unnoticed drilled the walls of two Customs warehouses at the Sofia Airport and steal the precious metal which was stored there.

The stolen gold, silver and platinum were seized by police in August during a crackdown on smugglers of metals, the minister said.

He added that the investigation is going on but for now it was clear that the alarm system of the warehouses has been switched off.