The driver of the tanker was taken to Waikato Hospital by ambulance with moderate injuries.
A Matamata fire crew was at the scene, while a HAZMAT (hazardous materials) team was on its way over the Kaimai Ranges from Greerton Fire Station in Tauranga to deal with the clean-up.
It's believed there were no other vehicles involved in the crash.
Police have advised motorists to expect delays after the incident.
"The recovery of the tanker and its load will require heavy salvage equipment and is expected to take some time," Mr Underwood said.
"To compound issues further, this part of Firth St is part of SH27 and is favoured by a lot of heavy transport operators transiting between the Bay of Plenty, Waikato and Auckland."
Mr Underwood said at this point northbound traffic is being allowed to continue along SH27 while southbound traffic is being diverted from Broadway through Burwood Rd and motorists should expect delays.