Police believe the horses escaped the Kaleen Holding Paddocks after a back fence chain was cut.

Their owners pay to keep them in the communal paddock run by Territory Agistment.

Caitlin Cameron was in her car with her two young children and partner when the horses stormed towards them.

She quickly pulled out her phone to take a video.

"It's not every day you see horses run towards you," she said.

"I don't think I've even been that close to horses before."

Ms Cameron's video of the horses trotting down a road past traffic went viral on the weekend.

"It's extremely unusual that all of the horses left the paddock at the same time. We've never had that before," said the head of Territory Agistment, Ryan Walsh.

"If we have a storm or something like that, it might be one or two horses get out, but [normally] never the whole herd."

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Watson resident Dylan Palmer saw his horses Franko and Oscar leading the pack the same way the rest of Canberra did.

"I saw it on Facebook, and then I saw the email about the horses out and I freaked out," Mr Palmer said.

"I thought they were going towards the highway and I thought, this is going to be disastrous."

Mr Walsh said the horses travelled from the paddock at Ellenborough Street down Maribyrnong Avenue to Baldwin Drive.

The animals are now "safe and sound" in the paddock, but one owner believes their horse flipped over and pulled a muscle.

Mr Palmer said when he got home from a trip to Dubbo on Sunday, the first thing he did was check the horses.

"They were settled in again, you could tell they were sweating quite a lot from having an adventurous time out on the streets," he said.

Mr Walsh wouldn't speculate what caused the mass exit, but said horses who are spooked tended to bolt.

"They are a herd animal so they tend to stick together, and their first response is flight. So they will, if they're spooked by something, they will tend to take off," he said.

"We've had similar incidents in the past.

"People get firewood, motorbike riders go through different areas. We've got problems with bike tracks being built and cubby houses and that sort of stuff as well."

He said it was lucky no humans or horses were injured.

"It was just so fortunate that there were no traffic accidents as a result of the horses moving along the road. It's just a really dangerous environment all around," he said.

Mr Palmer said he hoped it was a one-off event.

"I have no idea why anyone would want to purposely let out 20 horses into the public," he said.

"I just hope whoever's done it isn't silly enough to do it again because it can cause serious [injury or] death to both horses and people."

ACT Police said they determined the chain had been cut and urged anyone with more information to call Crime Stoppers on 1800 333 000.

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