Officials with the Houston Fire Department believe the fire started at an auto repair shop and spread to the warehouse.

About 500 gallons of pesticides were stored at a Houston warehouse complex consumed by a large blaze Thursday, an HFD official said. Firefighters continued to extinguish on-going flare-ups and hotspots on Friday.

Authorities on the scene are trying to determine how much ran off into nearby creeks.

Fire Cpt. Ruy Lozano said on Friday that it’s not clear how much of the pesticide was burned in the fire and how much leaked into adjacent waterways, but that drinking water is safe.

Spring Branch Creek is boomed off at I-10, just west of Wirt to catch the red runoff from the 4-alarm fire.#khou pic.twitter.com/u8N3fyWN5p — The Bishop (@BillBishopKHOU) May 6, 2016

Officials are asking residents to stay away from water run-off to nearby areas.

"The area of Spring Branch Creek and surrounding ditches and culverts should be avoided until authorities complete testing and deem them safe. Diking and boom operations are currently underway along with environmental contractors on sight performing environmental cleanup," officials said in a news release.

Environmental contractors said they have contained the petroleum additives along Spring Branch Creek.

The pesticides are water soluble and contractors are unable to contain or remove it. They are currently testing Spring Branch Creek for pesticide contamination levels.

Residents are advised to avoid impacted areas of Spring Branch Creek and affected ditches, canals and culverts. pic.twitter.com/UUauFAaAis — HCFCD (@hcfcd) May 6, 2016

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