A hazardous materials incident has prompted fire crews to evacuate the social sciences building at UC San Diego.

San Diego Fire-Rescue officials say two unknown chemicals mixed by staff members in a school chemistry lab, possibly creating explosive material.

An SDFD hazmat team and bomb squad were called in around 5:50 p.m. to deal with the situation. Once on scene, they ordered that the building be evacuated and that those in adjacent buildings shelter in place.

Roads in the area were closed as a precaution.

However, by 8:30 p.m., the SDFD crews began downgrading the response as the threat no longer posed a problem.

They have since handed operations over to the UCSD hazmat team, which will dispose of the chemicals.