Motorists are requested to slow down as they descend the hill just before Robertson to avoid further accidents.
This follows a HAZMAT (release of substance that could harm people) incident on Saturday morning, about 5kms from the town of Robertson.
The Cape Winelands District Municipality said its Fire Services have had a busy morning in the Langeberg valley.
Officials from Spil-Tek are trying to manually scoop up diesel from the broken tanker into a spare tanker.
This process is expected to take between 4 and 6 hours.
The Municipality said a stop-and-go, managing traffic flow will remain in place.