SPOONER, Wis. (AP) -- People evacuated after a chemical plant at Spooner exploded Tuesday have been allowed to return to their homes and businesses.

A hazardous materials team from Superior ran tests for chemical contaminants in the air.

Emergency officials announced just before 5 p.m. the team found the air posed no threat to people.

Two inspectors from the Occupational Safety and Health Administration are investigating.

State Department of Natural Resources workers also plan to perform soil and water tests.

Two people who were in the Cortec Corporation plant were injured when the explosion occurred just before 9 a.m.

They're believed to have suffered first- or second-degree burns.

Four other workers were not hurt.

The Wisconsin State Patrol says it hasn't determined the cause of the blast, which destroyed much of the building.

The plant made aerosols and paint solvents, but it appeared no hazardous chemicals were involved in the fire that broke out.