Officials say more than 350 prisoners are missing and presumed dead, although some of those who are unaccounted-for may have escaped.

The head of Honduras' prison system, Danilo Orellana, says the fire broke out late Tuesday in the town of Comayagua, north of the capital, Tegucigalpa. He said authorities are looking into whether it was caused by a prisoner or an electrical short circuit.

Authorities say many of the inmates burned to death or suffocated in their cells.

Distraught relatives surrounded the prison Wednesday morning, desperate to learn the fate of their loved ones. Some threw rocks at police and tried to force their way into the facility. Police fired tear gas in an effort to hold back the crowd.

The Organization of American States is sending a delegation to investigate. OAS Secretary General Jose Miguel Insulza expressed "deep consternation regarding the tragic events" and expressed solidarity with the government.

The Comayagua prison housed about 850 prisoners.

Honduran prisons are notoriously overcrowded and are often the scene of riots and clashes between rival gang members.  The U.S. State Department has criticized Honduras for "harsh prison conditions." The Central American nation's last major prison fire struck the town of San Pedro Sula in 2004, killing more than 100 prisoners.