BUENOS AIRES, Aug. 5 (Xinhuanet) -- Four days after the fire that destroyed a supermarket on the outskirts of Asuncion and killed some 500 people, forensic experts of Paraguay, Argentina, Colombia and the United States started Thursday the investigations to determine the cause of the incident.

    "We don't rule out any hypothesis because the investigation has just started," Teresa Sosa, the prosecutor for the case, told the press at the coordination center set up by the parking lot of the destroyed Ycua Bolanos supermarket.

    Preliminary investigation started Wednesday, when the building was completely searched to make sure no more corpses remained nor evidence that could help to determine the cause of the fire left unchecked.

    Agent Benedicto Perez of the Argentine province of Formosa, in the border with Paraguay, assured that the possibility of an attack was ruled out and, in principle, the fire could be an accident.

    His views echoed those of Paraguay's Interior Minister Orlando Fiorotto, who labeled the incident that has left 504 dead and 500 injured as "accidental."

    The agents sent to the spot of the fire are specialists on investigations of fires, explosives and counter-terrorism. They are commanded by Oliver Miller, who in the first analysis determined it was a "structural fire," developed in the natural conditions of the enclosed building.

    The forensic experts will work on the following tasks: the origin and cause of the fire, the security of the spot and finally,the logistics for the removal of the residues.

    Nine agents of the United States Alcohol, Tobacco and Firearms Agency (ATF) arrived Thursday in Asuncion to join the team of investigators, which added the number of agents from that country in Paraguay to 12, according to information released by Paraguayandaily ABC Color.

    Sosa explained that the first thing is to remove the animal and vegetal remains located in the food area of the supermarket, which are in an advanced state of putrefaction.

    On Wednesday, Spanish forensic doctor Juan Cartagena warned that there was a risk of infection in the area due to the decayed remains.

    The fire broke out when the supermarket was crowded with Sunday midday shoppers. Reports said nearly 1,000 people had been inside the shopping center, which is part of the complex that also houses offices and an underground parking lot. Enditem