A heavy blizzard dumped wet snow on volunteers Wednesday as they rushed to build dikes against rising flood waters in North Dakota, as officials used explosives to try break up ice jams on swelling rivers.

President Barack Obama issued a federal disaster declaration for 34 counties and two Indian reservations as the entire state remained under a major flood warning.

The storm's blustering winds knocked out power to towns across the largely rural prairie state and made many roads impassable as it dumped snow and freezing rain, officials said.

Several bridges and roads were already closed due to flooding as an unusually heavy snowpack began to melt on top of saturated land that has not yet fully thawed.

"The state has turned into a fishing pond and can't absorb any more snow or rain," said Patrick Slattery of the National Weather Service.

More snow was forecast to fall on the Red River valley in the coming days and rain could worsen flood conditions by the weekend, the weather service predicted.

Low-lying homes across the state were evacuated as rivers and creeks spilled over their banks, although damage was largely restricted to water in basements. No injuries were reported in a situation report issued at 7:30 pm (0130 GMT Thursday).

About 20 people from homes south of Fargo were evacuated with airboats that sluiced through ice-covered floodwaters after sandbag dikes began to leak.

"Frankly I do expect more (evacuations) over the next 24 hours," said Dave Rogness, the Cass County emergency manager.

A farmer stranded on his tractor and several families whose rural homes were surrounded by floodwaters were also rescued across the state. Officials also evacuated 146 inmates from a jail in the state capital of Bismark, where the Missouri river was rising quickly as a result of a massive ice jam that stretched all the way to the border with South Dakota.

The governor called in military specialists to try break up the ice jam with explosives after fragments of ice as big as four feet (1.2 meters) thick and other debris got stuck on a sandbar.

Blackhawk helicopters were to be used to dump sand and salt down river of the ice jam to help get the water flowing again and reduce flood pressure on the city. Officials warned they may not know if the operation was successful until Thursday.

Heavy snowfall prompted thousands of volunteers in Fargo to reinforce temporary dikes and levees after the projected crest of the mighty Red River was raised to a record 41 feet (12.5 meters) by Saturday.

"It kind of scares you a little bit when they do that," Stephen Garrity said of the rising projections as he scrambled to add sandbags to dikes around his home.

The river, which is normally only about 98 feet (30 meters) wide, was rising about an inch (2.5 centimeters) an hour, yawning to swallow trees along its banks -- it appeared to be some 2,952 feet (900 meters) wide.

A sandbag dike stretched for miles along the edge of the floodwaters.

Snowplows cleared streets for trucks delivering sandbags to neighborhoods along the river, where volunteers from as far away as Iowa and Montana mingled with high school and college students whose classes were cancelled.

Hundreds of volunteers passed along sandbag after sandbag, some standing on pieces of wood to protect against the deep mud under the trampled snow.

"All the national media stories are, 'Oh, they need help.' So here we are," said Rick Spohnholtz of Newark, Illinois, who arrived with his 13-year-old son Ricky on Wednesday morning.