The townhall in the southern town of Kroumovgrad has declared December 7 2009 a day of mourning because of the tragic death of three teenagers who died two days earlier when military explosives detonated.

The three boys, aged 13, 15 and 16, activated the explosives in their room at the local boarding school.

Two of the boys were killed on the spot while the third died later in hospital.

As a result of the tragedy, police arrested four people, all of whom employees of the boarding school.

One of the main leads police were working on, was that the explosives were given to the boys by someone who takes care of the building heating system. Allegedly he gave them the explosives as a reward for the work the three boys had done at his house.

Not knowing or realizing what it was, the thee boys started playing with the explosives when it exploded, police believed.

After the man was arrested, police found a number of military explosives at his house in the town. Allegedly the man attempted to kill himself with a pocket knife when police went in to arrest him.

The boarding school director has also been arrested together with two other employees, all of whom will be investigated for poor control at the school which had allowed the three boys to bring the explosives into the home.

An investigation into how the military explosives ended up with the suspect was underway. Interior Minister Tsvetan Tsvetanov was quoted by Focus news agency as saying that an employee of the local army barracks had smuggled anti-tank charges out the barracks.