Relatives of the victims and survivors of the fire wanted a murder conviction (25 year prison term) for three men the owner of the supermarket, his son and a security guard, who were accused of locking the doors when the blaze broke out.

Angry relatives threw chairs at the judges and shouted corruption when they told the courtroom they had convicted the three of the lesser charge of involuntary manslaughter, (which carries a maximum prison term of seven years). The violence immediately spilled into the streets of Asuncion's commercial district.

Riot police armed with riot shields, water cannons and tear gas fought to quell the unrest but where overrun by crowds in a rampage. However official reports indicate that at least 31 people had been injured plus over fifty arrests.

During the rampage hundreds of rioters stormed into a supermarket belonging to the same chain where the fire took place in August 2004.

"In spite of the confusion, the police practically have control of the situation" Interior Minister Rogelio Benitez told the Asuncion television late evening.

Paraguay’s worst peacetime tragedy broke out in a grill restaurant in the vast Ycua Bolanos supermarket on the outskirts of the capital. The fire quickly spread, causing the roof to collapse and engulfing an underground parking area. The fire killed an estimated 400 people and seriously injured 500 when allegedly the owners locked the doors fearing looting.

The three people convicted on Tuesday were the firm's main owner Juan Pio Paiva, his son Victor Daniel Paiva and security guard Daniel Areco. They pleaded not guilty, denying the doors had been shut to prevent looting and saying victims had not been able to escape because of the speed with which the flames and toxic gases spread.

Prosecutors said the building was not equipped with proper fire escapes or alarms.