TUSTIN, Calif. (AP) — Parks and schools were closed Thursday in a Southern California city after officials found asbestos in the charred debris of a historic World War II-era blimp hangar.

The city of Tustin closed at least nine parks and urged residents to limit outdoor activities to reduce their exposure to ash after asbestos was detected in preliminary samples of ash and debris.

The city also declared a state of emergency over concerns that asbestos and other chemicals could have polluted the air. The declaration said that possibility posed “conditions of extreme peril to the safety of persons and property” that only local, state and federal efforts can mitigate.

Southern California air quality regulators will continue to analyze samples from areas around the hangar for toxic gases and metals, the city said in a statement.

Schools were closed Thursday to ensure student safety in the Tustin Unified School District some 35 miles (56 kilometers) southeast of Los Angeles. A Veteran's Day event planned for Saturday was canceled.

The blaze broke out early Tuesday at the massive wooden hangar, which was one of two built in 1942 by the U.S. Navy to house military blimps. The cause of the fire was under investigation.