One lane of the road had reopened when a second crash happened, at 9.50am, nearby on SH5, involving two cars and leaving three people with moderate injuries.
Leidy Monslaves was headed to Matamata when she was stopped by the blocked road.
"We were stuck for more than 20 minutes then we saw police racing off to the other crash."
She said it was "really icy" out on the road and the grass was completely white.
"When I got out of the car, it was really slippery.
"It is scary being out on the road like that, there are a lot of drivers who still go too fast."
MetService meteorologist John Law said Rotorua was in for a few more frosty mornings.
"With the water that's come through ground surfaces are wet and dropping to -1C or -2C.
"Those are the perfect conditions for cold and icy roads."
He said the temperature had peaked at 10C today but would drop again overnight meaning more icy patches in the morning.
The cold weather would continue through to Saturday morning and he urged drivers to take care on the roads.
New Zealand Transport Agency Bay of Plenty systems manager Rob Campbell said there were a number of crashes in the vicinity of Rainbow Mountain this morning caused by black ice.