There are no plans to shut down a cycle path in Palmerston North after a toddler was killed in a collision with a motorbike, the city's mayor says.

A family of five were riding their bikes on the Longburn shared cycle and walking path alongside Pioneer Highway when a motorbike reportedly ploughed into them, just before 7pm on Friday.

Three people went to hospital, one of them in a critical condition, emergency services said at the time.

On Saturday police confirmed a two-year-old had died.

Police have previously referred to the family as pedestrians but have now confirmed they were on bikes.

Images from the scene showed what appeared to be a motorised dirt bike, as well as an adult's bike with the front wheel bent.

That bike had a child's seat attached to the central bar, between the rider's seat and the handlebars. It's not clear where the toddler had been riding.

Palmerston North Mayor Grant Smith said the police investigation into the tragedy was still under way and he couldn't comment too much. But he understood it was dusk and the motorbike rider and the family didn't see each other until it was too late.

"It's just a horrible thing that happened."

The 4km Longburn shared path is adjacent to Pioneer Highway, southwest of Palmerston North. It stretches from the city to the industrial village of Longburn and is well used by workers and schoolchildren.

The motorcyclist - who Smith said was on a dirt bike - should not have been using the pathway, he said.

"It crosses some rural residential properties. But it's still a pathway for cyclists and pedestrians, not motorcycles.

"He shouldn't have been there under any circumstances."

Smith said there was some "media chatter" about shutting down the path but said that would not happen. Until now the path had been a good news story about getting kids and workers into active transport modes.

"We'll find out what's gone on but there's no question of closing the pathway or putting up bollards," he said. Changing bylaws following the incident would be "legislating for one idiot".

Smith understood the dirt bike's rider had been wearing a helmet. He was now in hospital, as was the father of the family.

"That's the other tragic thing too - there's no winners here. He'll be scarred for life. And I believe he's a young man and it will affect his family."

Manawatu police area investigations manager Detective Senior Sergeant Craig Sheridan said police were working closely with the Coroner and the family of the 2-year-old.

"We are satisfied we have identified all of the parties involved and we expect to speak with them in the coming days," Sheridan said.

An update was expected later next week.