Workers reportedly spilled large amounts of a chemical which they feared was radioactive in a pathology reference laboratory, located at 2250 East Alcazar Street. The building is located on the Health Sciences Campus, which is a 15-minute drive from the main USC campus.
Employees were tested and all showed negative for radioactivity. No injuries or illnesses were reported.
The first floor was reopened just before 5 p.m. but the second floor remained closed.
An investigation was underway.