SAN ANTONIO -- All lanes in both directions are closed on US 281 between Jones Maltsberger Road and Loop 410 after an 18-wheeler jackknifed and overturned on the northbound side.

The truck flipped on US 281 southbound and spilled white gravel across both lanes, causing the closure.

Traffic is moving slowly on US 281 and being diverted to the access road. Southbound is being diverted to Sunset Road and northbound to the 410 ramp.

Crews are onsite and cleanup could take a couple of hours.

An SAPD spokesman said the gravel trailer came unhitched from the cab, but the driver did a good job of keeping this from being worse.

He said three cars sustained gravel damage, but no people were injured.

For updates, visit KENS 5 Traffic.