The main lanes of Interstate 37 South near Loop 410, as well as the ramps, are back open after a Tuesday night chemical spill.

Hazmat teams had been cleaning up the site since around 6:45 p.m. Tuesday when an 18-wheeler carrying roughly 3,500 gallons of sodium hydroxide overturned while merging onto I-37 south from Loop 410.

Only three of the containers in the first rig leaked, and firefighters said those leaks were minimal.

As a result of the initial spill, police to shut down all lanes of I-37 South at 410 and both the east and westbound ramps from 410 onto 37 South.

Police said it was unclear what caused the big rig to overturn.

The driver of the overturned 18 wheeler was taken to a hospital as a precaution. His injuries did not appear to be serious, according to police.