The southbound lanes of Interstate 35, north of Laredo, are now open after being shut down for a few hours this afternoon. Local and state police officers were forced to close the roadway following the accident involving a flipped over 18-wheeler. Traffic had to be diverted to the frontage road as the mess was cleaned up. The Texas Department of Transportation says the crash happened when the tractor-trailer collided with the metal beam guardrail fence, which caused to the big truck to flip over on its side. Strewn metal could be seen from both the big rig and guardrail. No on was seriously injured in the accident and I-35 southbound is now reopened.