One lane along part of Old Taupo Rd will be closed for several weeks after a hole was discovered.
The NZ Transport Agency Bay's of Plenty highway manager, Niclas Johansson, said the northbound lane of State Highway 5 (Old Taupo Rd) was closed from 2pm yesterday to allow contractors to use a camera to establish the extent of the problem.
The hole was found near the Utuhina Bridge at the weekend.
The speed limit on Pukuatua St near Rotorua Boys' High School has been reduced to 30km/h.
Contractors said the hole was about 3m deep.
"At this stage we are still determining the extent of the issue, however we are focused on finding a solution as quickly as possible to minimise disruption," Mr Johansson said.
"We have closed a lane to ensure motorist safety and to prevent vehicles from damaging the site until we can complete emergency works to repair the road."
The closure affected the lane through the State Highway 5/State Highway 30A (Pukuatua St) intersection and would cause queuing and delays for travellers, Mr Johansson said.
"It is likely the lane closure will remain in place for a number of weeks while we complete emergency works. [State Highway 5] is the main route to Hamilton and Auckland so we encourage people to plan for delays when travelling north through Rotorua," he said.
Motorists wanting to avoid the area can travel to the CBD via Malfroy Rd and Ranolf St (northbound traffic) or via Lake Rd and Ranolf St (southbound traffic).
"We expect to have information this week which will enable us to make some decisions on the type of emergency works we will need to do," Mr Johansson said.
"Fixing any problem in this area will involve large machinery and excavation to fill the hole, no matter what size it is, so unfortunately there will be disruption to traffic.
"The Transport Agency apologises for any inconvenience and thanks drivers for their patience and understanding at this time."
For information on conditions and incidents: www.nzta.govt.nz, 0800 4 HIGHWAYS or follow @nztawaibop on Twitter.