HOUSTON (AP) - The Latest on a fire that had been burning at a Texas petrochemical storage facility (all times local):

9:25 a.m.

Authorities say it appears that the suppressive foam firefighters are using at a Houston-area petrochemicals storage facility is separating at times and allowing dangerous benzene vapors to escape before another layer of foam can be applied.

Harris County Fire Marshal Laurie Christensen said at a news conference Thursday that crews are applying layer after layer of foam where several storage tanks burned at the Intercontinental Terminals Company in Deer Park, southeast of Houston.

The fire began Sunday and was extinguished Wednesday, but a flare-up occurred later Wednesday that crews are working to prevent from occurring again.

Authorities say winds are light Thursday so the vapors aren't spreading beyond the immediate area of the ITC plant.

They say orders to stay indoors are being done "out of an abundance of caution."

At least three area school districts cancelled classes Thursday.

8:10 a.m.

National Guard troops have been called in and residents are being told to stay inside after elevated levels of benzene were detected near a Houston-area petrochemicals storage facility that caught fire this week.

Harris County officials said Thursday that the Guard and hazardous materials teams have established perimeters around the Intercontinental Terminals Company in Deer Park.

The Texas Environmental Protection Agency said Wednesday that benzene levels near the facility didn't pose a health concern. But authorities now say a shelter-in-place order following "reports of action levels of benzene or other volatile organic compounds" within Deer Park.

Several school districts also canceled classes for the day, citing "unfavorable air quality conditions."

The fire started Sunday, sending a huge, dark plume into the air, and spread to storage tanks holding components of gasoline and materials used in nail polish remover, glues and paint thinner.

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