A rollover crash slowed afternoon traffic Wednesday in the westbound lanes of LBJ Freeway near Marsh Lane.
The conditions of those involved in the collision and the cause of it are not yet known.
The crash has closed the two left lanes and only one lane of traffic is getting through.
Drivers are advised to expect major delays. At 4:15 p.m., the backup was estimated at five miles and will take about 45 minutes to pass through.
The roadway reopened to traffic at about 5:15 p.m.