Cambridge Road in the Waikato District is closed after a truck rolled.
It happened just before 1:30pm between Parallel Road and Lamb Street, says a police spokesperson.
"The sole occupant of the truck is currently trapped - their injury status is not yet confirmed.
"There is a possible chemical leak from the truck, which is being dealt with by Fire and Emergency NZ."
Police are at cordons until the all clear is given from FENZ.