Romulus, Mich. ? A fire raged at a suburban Detroit chemical plant Tuesday night, forcing police to evacuate homes in a half-mile radius.

Authorities said no injuries were reported, and no one was inside the plant when the fire started.

Witnesses described a series of loud explosions that shook the ground and shot flames and smoke into the air.

Romulus Police Chief Charles Kirby said it was unclear what hazardous materials might be involved in the fire, but he urged residents within the half-mile radius to evacuate because materials in the smoke could pose a danger to their health.

Kirby said fire officials were waiting for a helicopter to take them above the fire to help devise the best strategy for fighting it.

Romulus, home to Detroit Metropolitan Airport, is about 25 miles southwest of Detroit.