Updated

Venezuelan authorities say the blaze that killed 68 people in a police station jail likely started when inmates set fire to their mattresses.

The comments Monday by Chief Prosecutor Tarek William Saab were the first to suggest a cause for the last week's horrific fire in the city of Valencia.

Saab told Union Radio that overcrowding contributed to the tragedy and promised that prison authorities will be held responsible even if they didn't instigate the fire.

Five officers including the sub-director of the police station where the fire happened have been arrested.

All but two of the dead were detainees. Some family members of those killed have said their loved ones telephoned before the fire and said their jailers were pouring gas in the cellblock.