Emergency officials say hazardous materials have been released into the air from a warehouse complex fire in Houston that’s generating towering plumes of black smoke.

City officials issued an alert Thursday ordering people in nearby homes and businesses to stay inside, close all windows and shut off any air conditioning.

The Houston Fire Department didn’t immediately say what hazardous materials may have been released during the fire and explosions that rattled the industrial area. But the department says no injuries have been reported.

Authorities have not said what they believe started the blaze in west Houston.

Students at a nearby elementary school were evacuated, though police at the Spring Branch Independent School District say all of the children are safe.

#SpringBranch ISD: 650 students, 80 staff rushed on 11 buses to Don Coleman Coliseum on N Dairy Ashford. @KPRC2 pic.twitter.com/2yTT4VZN6V — Brandon Walker (@KPRCBrandon) May 5, 2016

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