Raleigh, N.C. — At least one mortar shell exploded Tuesday morning after it got mixed in with a load of scrap metal at a processing plant on Garner Road, police said.

Witnesses said they heard two explosions and saw some smoke at Raleigh Metals Recycling, at 2310 Garner Road, at about 11 a.m.

Plant owner Greg Brown said the force of the explosion knocked one worker over, and a second worker complained of ringing in his ears. Isai Bravo Santiago, 33, and Adrian Bravo, 27, were taken to WakeMed for treatment.

The explosions didn't result in any chemical release or fire, Brown said.

The explosions prompted Raleigh firefighters and bomb and hazardous materials experts from the Raleigh Police Department to respond to the area.

"Some sort of military ordnance had found its way into the recycling center, and ... at least one round of that ordnance had exploded," said Jim Sughrue, spokesman for the Raleigh Police Department.

Preliminary reports described the explosive as a mortar shell, Sughrue said. An unknown number of mortar shells were in the load of metal being processed, and it was unclear whether any more were live rounds, he said.

Ordnance experts from Fort Bragg inspected the plant Tuesday to help identify the explosive, Sughrue said

Brown, who bought Raleigh Metals Recycling last August, said the company has a prohibition against purchasing ammunition. He said he wasn't sure how the mortar shells got into the mix.

Portions of Garner Road were blocked off and nearby businesses and residents were evacuated.

The Garner Road YMCA and the Biltmore Hills apartment complex are across the street from the scrap plant.

"When you hear something like an explosion in this day and time, you wonder what it is and just pray for people's safety," said Glendora Alston, a manager at the Biltmore Hills complex.

Agents with the FBI and the federal Bureau of Alcohol, Tobacco, Firearms and Explosives have been contacted, but Sughrue said no determination has been made as to which agency would investigate the incident. Authorities are waiting for information from the Fort Bragg experts, he said.

State Department of Labor investigators also were reviewing the incident.

Raleigh Metals Recycling was cited by the Labor Department in November 2003 for not providing a safe environment for employees, a missing safety guard on machinery and four minor violations.

According to the company's Web site, Raleigh Metals Recycling is a scrap metal processing facility that provides recycling services. It sits on 19 acres of land south of the Interstate 440 Beltline and has about 40 employees.