WIXOM, Mich. -- Wixom police and fire crews evacuated businesses in the area of Downing Road and Wall Street because of a chemical spill Tuesday afternoon.

Police said about 500 gallons of nitric acid spilled at the Tronex Chemical Company around 3 p.m. in the area of Downing Road near Wall Street, closing down the roads in the area.

The roads reopened Wednesday morning.

Witnesses told Local 4 News that they saw yellow smoke rising from the plant. Authorities said that nitric acid oxidizes when it hits the air and creates a yellow smoke.

Officials said nitric acid is a highly corrosive and toxic acid that can etch concrete and metal and can cause severe burns.

Authorities closed Wall Street and West Road on Tuesday afternoon while they conducted air samples.

Two Tronex employees suffered minor injuries.

Wixom's Director of Public Safety said the acid was as thick as 3 inches deep in some parts of the building and the cleanup was difficult and slow.