Six visitors to Fort Edmonton Park were injured, one seriously, after a horse-drawn wagon overturned on Wednesday.

Alberta Health Services spokesperson Kerry Williamson said six emergency vehicles responded to the incident, transporting six adults to area hospitals.

One patient is in serious condition and the remainder are in stable condition, Williamson said in an email.

The cause of the incident is not known, said Darren Dalgleish, president of Fort Edmonton Management Company. It happened near the fort structure just before noon, Dalgleish said.

"A carriage pulled by two horses had turned over, and [there were] multiple injured passengers that had obviously fallen out," he told CBC News.

"I don't know the degree of seriousness yet."

The old-fashioned wagon ride is one of the park's attractions. The wooden cart, with bench seating that faces inwards, travels a loop around the pond that takes about 10 minutes.

Dalgleish said he believed there were between seven and 10 guests on board the wagon when it turned over.

Darren Dalgleish, president of Fort Edmonton Management Company, said Thursday a thorough review of the crash is underway. (CBC)

Dalgleish noted that he is still quite new to the organization but said he hasn't heard of anything like this happening before.

"Rare is putting it lightly," he said.

"I've never heard of this happening, long-term staff have said this has never happened before. But again, we're speculating on what happened, and it's impossible to tell the details about it at this time."

Dalgleish said his first concern is for the condition of those taken to hospital. Then he will begin interviewing staff — including the driver — to find out what happened.

"Right now, what I'm concerned about is getting the status of the passengers and making sure they're OK, and as soon as we get past that point, we'll be digging into the details of the incident," Dalgleish said.

He said the wagon's driver was also taken to hospital by a colleague, as a precaution.

He commended emergency crews including fire trucks and ambulances, who were on scene "right away" and helped bring calm to the situation.