UCLA’s Molecular Sciences Building was evacuated for about nine hours Thursday afternoon after “an environmental hazard” was reported, the university said on Twitter.

The announcement, made just after 1 p.m., was followed by a request that students, staff and the public avoid the area and news of a road closure.

“Charles E. Young Dr South remains closed between Tiverton Dr & Manning Dr.,” UCLA said on Twitter. “Expect traffic delays and transit reroutes around Parking Structure #2.”

As of just after 5 p.m., the cleanup efforts were ongoing, and the building had not been reopened.

“There are no reported injuries or immediate threat associated with this incident. At this time, the incident is stable,” the Los Angeles Police Department said on Twitter.

It wasn’t until 10 p.m. that the building was cleared and reopened, the school said.

No injuries were reported, and the substances that caused the lockdown has not yet been identified.