Sanford, N.C. — A fourth man has been detained in connection with the discovery last week of military explosives at a Raleigh scrap-metal recycling plant, police said Thursday.

Manuel Sanchez Uriosteget was being held by U.S. Immigration and Customs Enforcement agents, said Capt. David Smith, of the Sanford Police Department.

Almost three dozen military explosives were found and detonated at Raleigh Metals Recycling last week. Plant owner Greg Brown said a customer sold the munitions to the plant with other scrap metal, and his workers didn't recognize them as live ammunition.

Two workers sustained minor injuries when one of the shells exploded as a load of scrap was being processed, and a team of munitions experts from Fort Bragg detonated other devices over the next four days.

The process forced nearby residents from their homes and required a portion of Garner Road to be shut down for much of the week.

Uriosteget lives in the same mobile home park as Adrian Nunez-Aviles and brothers Javier Gomez-Urieta and Salvador Gomez-Urieta, who were arrested a week ago on immigration violations and have been held for questioning in the munitions case.

A search last week of a mobile home on Carver Drive in Sanford turned up artillery shells in the yard similar to the ones that were dropped off at Raleigh Metals Recycling, including two live rounds.

A search of Uriosteget's trailer also turned up ammunition, Smith said. Investigators located anti-tank weapons, spent 2-millimeter shells and .50-caliber bullets in a yard at the trailer park, he said.

The FBI and the federal Bureau of Alcohol, Tobacco, Firearms and Explosives also are investigating the case.