The Assiniboine Park Conservancy says over 13,000 rubber ducks were dropped from a crane into the Assiniboine River on Saturday for The Great Manitoba Duck Race.
The race was meant to raise money for the conservancy as well as the Assiniboine Park Zoo.
But at the end of the race, the conservancy says the oil booms used to capture the ducks failed.
"The current was extremely strong and there was high winds. Because of that, some of the ducks made it over the barrier," said Laura Curtis, a spokeswoman for the conservancy.
"I would say over half made it over the barrier."
The conservancy says in a news release that Manitoba Conservation has been informed of the incident, and that officials responded that the ducks don't pose an environmental threat.
Staff with the conservancy spent much of the weekend walking the Assiniboine's riverbanks, scooping up the ducks with nets.
On Saturday, Curtis said even the city's firefighters were helping.
"They were concerned that children or the general public would try to grab the rubber ducks and would be putting themselves in danger," she explained.
Most of the ducks had been recovered by Sunday afternoon but the conservancy says it is planning to keep looking this week.
The ducks are harder and heavier than bath toys. Curtis said they're special racing ducks that were rented from a U.S. company, so the conservancy is eager to get as many back as possible.
The conservancy is asking people who spot pockets of rubber ducks to call them, and not risk their own safety by retrieving them on their own.
Curtis said as far as she was aware, none of the ducks made it past The Forks and into the Red River.
If they had, Curtis conceded it was possible they could float all the way to Lake Winnipeg.