An ice breaker works to ease the flow on the Red River. (CBC)

An ice jam north of Winnipeg that had backed up the Red River and caused flash flooding in several communities was dislodged Thursday morning.

The river is now flowing rapidly, but officials aren't ready to say the flood risk is over. People living upstream should be warned there could be more danger of flooding as the ice works its way north.

Manitoba Water Stewardship spokesman Steve Topping said it is "very likely" the ice will reform and jam again, probably somewhere north of the Lockport dam. He said survey crews are being sent out to determine where that might occur.

Four rural municipalities just north of Winnipeg — St. Andrews, St. Clements, East St. Paul and West St. Paul — all declared states of emergency on Wednesday. The Red River Floodway usually protects those communities, but the ice jam prevented the water from moving, causing it to flood the banks.

Some homes flooded to main floor

The flooding forced 30-40 families from their homes in St. Andrews, where the water in a number of residences rose above the main floor. Emergency measures organizers were advising many more homeowners to be ready to leave.

In East St. Paul, as many as 100 homes in the neighbourhoods of Highland Park and Whitby Harbour, as well as homes along Henderson Highway, were on high alert. Overland flooding in the municipalities was washing out roads and filling yards.

Emergency crews worked through the night Wednesday and into Thursday morning, bringing in huge chunks of limestone rock to fill in low-lying areas.

The province also deployed a second sandbagging machine, 100,000 additional sandbags and almost three kilometres of tube diking to the area.

Paul Guyader, the emergency measures co-ordinator for St. Andrews, told CBC News on Wednesday that equipment used to break up ice couldn't reach parts of the jam because it went right across the river.

"We've tried backhoes on both sides, but again, you're reaching 20 feet out from the roadways and this jam goes across the river where it's probably a quarter-mile wide," he said.

Alf Warketin, the province's senior flood forecaster, told Guyader he would likely have to wait for nature to take care of it. "The water would rise about three feet on the ice jam … and that pressure would probably move it along."

3 more communities under states of emergency

Three other Manitoba rural municipalities — Blanchard, St. Laurent and Franklin — also declared states of emergency on Wednesday.

Franklin is about 80 kilometres south of Winnipeg and Blanchard is northwest of Brandon. St. Laurent includes a number of communities in Manitoba's Interlake district north of Winnipeg near Lake Manitoba.

Those regions are also experiencing washed-out roads and flooded basements due to water backing up from ice jams and frozen culverts in the ditches.

Fargo doubling up on dikes

Meanwhile, south of the border in Fargo, N.D., a secondary earthen dike is being built to back up the primary dike, which officials are concerned may not be enough to hold back the water.

The crest of the flood is expected on Saturday, somewhere around 12.3 to 12.6 metres — above the devastating 1997 crest of 12 metres — and a record level in the area.

The level Thursday morning was already at 11.4 metres.