DALLAS — A midafternoon mishap on LBJ Freeway snarled traffic Monday as rush hour approached.

The Texas Department of Transportation said three westbound lanes of the busy highway were blocked by an 18-wheeler that jackknifed near Midway Road. Only one lane was getting through as arrangements were made to move the big rig.

Eastbound traffic was slowed by curious onlookers all the way back to Interstate 35E.

It was not clear whether any other vehicles were involved in the wreck or whether anyone was hurt.