CYPRESS, Texas (KTRK) -- A major rollover crash is blocking a portion of the Northwest Freeway on Wednesday morning, Lt. Terry Garza with the Harris County Sheriff's Office said.

Houston TranStar reported the incident involving a heavy truck on US 290 westbound before Spring Cypress at about 9:16 a.m. Garza said all westbound lanes in that area are being impacted.

Drivers are encouraged to seek alternate routes as heavy delays are expected.