EMBED >More News Videos Residents were forced to shelter in place during a 4-alarm fire in Spring Branch.

EMBED >More News Videos In this viewer-submitted video, flames and heavy smoke are seen in a huge four-alarm fire in Spring Branch

EMBED >More News Videos A woman says she's blessed her sister survived a massive fire in Spring Branch

HOUSTON (KTRK) -- The remains of the building look like a war zone, after a massive fire destroyed a warehouse in northwest Houston Thursday.A Houston Fire Department district chief says the massive warehouse fire began with a house fire call on Laverne Street in Spring Branch. He says a three-bay garage behind the home was burning with fire trucks arrived.By then, the fire had already crossed the fenceline to the adjoining industrial warehouse, A-1 Custom Packaging on Spring Branch Drive at Laverne Street, near Long Point Road. Minutes later, thick black smoke was spreading to the south and the Galleria area, and students were evacuated from Spring Branch Elementary."Some kids were crying because they were worried about their brothers and sisters," fifth grader Melina Cantero said.Melina Cantera was among the nearly 750 students and staff evacuated to Coleman Coliseum.No one was injured in the huge fire. Only one home, believed to be the one with the detached garage, had significant damage. Fire crews spent several hours and thousands of gallons of water protecting residential structures from the burning warehouse.One witness says her sister sent a text message right as the fire began. The text simply read: 'My shop exploded,' she said."All they heard was just a lot of pops, and then they started seeing flames," witness Susan said. "Then they started evacuating."Susan says her sister's shop was located next door to the packaging business that was consumed by the fire.The business where her sister works may now be a total loss, Susan says, but she's relieved her sister is alive."I'm very blessed," she said. "That's why I came over here, to see my sister."As of Thursday afternoon, the chemicals that resulted in a series of explosions haven't been made public. In a ditch that adjoins the property, pesticide and a dark red petroleum additive frequently used in diesel seeped into the runoff water. Crews are working to remove the additive, and are hoping the recent floods will dilute the pesticide.An alert has been issued for the immediate area, warning residents to avoid the ditch water. For pet owners, that means keeping your animals indoors, and keeping them away from ditches in the area.A HazMat team took samples of the substance and is now analyzing it.