HARRIS COUNTY, Texas (KTRK) -- A major wreck involving a concrete mixer is blocking a portion of Highway 99 in northwest Harris County on Monday morning.

Houston TranStar reported the incident at about 6:36 a.m., leading to a complete roadway closure on SH-99 Lanier/Grand Parkway North westbound after Cypress Rosehill Road.

SkyEye13 flew over emergency crews responding to the scene, where a concrete mix rolled over a ditch, trapping its driver, according to the Harris County Sheriff's Office.