Isabel Kallmeyer, 9, right, works with her neighbour Caitlin Carson, 6, to fill sandbags that will be piled around the Kallmeyer home in Fargo in the hope of holding back flood waters of the Red River. (Carolyn Kaster/Associated Press)Water levels upstream in the Red River along the Minnesota-North Dakota border dipped Tuesday, raising the spirits of sandbaggers struggling to build protective dikes to withstand possible record flooding.

The U.S. National Weather Service lowered its crest forecast for Wahpeton, N.D., and Breckenridge, Minn., downward to 5.4 metres by Wednesday morning, well below the tops of dikes in those cities.

Meteorologist Jim Kaiser called it "definitely good news," but cautioned it's still too early to say whether the river's projected crest at Fargo would be lowered.

The Red is expected to crest Saturday at Fargo at 11.9 to 12.5 metres. That's at least 15 centimetres above the record set in 1997.

An emergency dike around the city's downtown is being raised to 12.8 metres, but the expected crest could still threaten several neighbourhoods in lower areas.

Hundreds of volunteers were at work on sandbags, with a goal of filling nearly two million.

"We don't see any fear," Fargo Mayor Dennis Walaker said. "We just see people working very hard."

Volunteers, National Guard filling sandbags

Workers install a portable interlocking container system that will be used to help hold back flood waters from the Red River Monday in Fargo, N.D. (Dave Kolpack/Associated Press)American Red Cross spokesperson Maryann Sinkler said about 100 Red Cross volunteers are making sure people filling sandbags have food and water.

"Our role is to make sure that they have the food that they need … and that they stay hydrated because even though it's cold outside, they still need to stay hydrated," she said.

About 660 National Guard members have been mobilized, and businesses and schools are closing their doors so people can help fill sandbags.

"They have city buses collecting volunteers … and bringing them into places called sandbag central or taking them to locations along the river … to build sandbags," she said.

Along with providing old-fashioned shovels, the city is operating three machines capable of producing 15,000 sandbags an hour.

Fargo has also deployed a portable wall system that shielded troops in Iraq and Afghanistan from bullets. The system is made up of one-metre-high interlocking containers that are filled with sand. It took workers just half an hour Monday to set up about 300 metres of the containers.

With files from the Associated Press