FARGO (AP) - The Red River breached a dike today and sent water flowing into buildings at a school campus in Fargo in an episode the mayor called a "wakeup call" for a city that needs to be vigilant for weaknesses in levees that could give way at any time.

"The campus is basically devastated. They fought the good fight. They lost and there's nothing wrong with that," Mayor Dennis Walaker said. "Those things will continue to happen. I guarantee it."

Oak Grove Lutheran Principal Morgan Forness said city officials, the Army Corps of Engineers, and the National Guard unsuccessfully tried to contain the gushing water to one building after a flood wall panel at the school buckled around 1:30 a.m. But the water kept spreading and "we couldn't contain it. … it's inundating all of the buildings."

Authorities managed to largely contain the flooding to the campus, preventing more widespread damage in nearby areas. The breach occurred at a spot in the river where the current is especially fast, and the flood was so powerful that it shot water 3 to 4 feet in the air at times. "It just tells you the power of the river," said city commissioner Tim Mahoney.

The city had been bracing for a crest of up to 43 feet today, but instead learned Saturday that the river may already have peaked. The National Weather Service said the river crested at 12:15 a.m. Saturday at 40.82 feet.

By early today, the Red River had dropped to 40.15 feet, still more than 22 feet above flood stage. The river may fluctuate up to a foot and remain at dangerous levels for a week, meaning an agonizing several days before people can relax.

The flooding at Oak Grove Lutheran - heavily damaged in the 1997 flood - represents the type of flooding that could pop up in Fargo throughout the week, officials said.

"The main event is right now, while we have this higher water," said Rep. Earl Pomeroy, D-N.D. "And it ain't over til it's over. And it ain't gonna be over until several days from now."

To prevent further dike breaches, Fargo planned to begin dropping one-ton sandbags from helicopters today to deflect the violent current of the Red River and keep it from pounding vulnerable areas of the levee system. The aerial effort also includes Predator drones that are watching flood patterns and ice floes from the air and helping teams respond on the ground. It's the first time the drones have ever been used in a flood-fighting effort.

The city has requested more volunteers to resume sandbagging today, and many were expected to turn out after church services in Fargo, a heavily Lutheran town of more than 90,000 residents. The mayor began a briefing this morning with a prayer, and Gov. John Hoeven encouraged everyone "to say a prayer for everyone in harm's way."

Triumph Lutheran Brethren Church planned to hold its Sunday services at a Ramada hotel to accommodate all the other churches that canceled worship because of the flood. Their service would be pared down - no high-tech PowerPoint, no food, no Sunday school, said church member Tami Crist.

"It'll be just prayer, some old hymns everybody knows, and being together," Crist said. "We've sandbagged a lot of people's homes, they're safe for now. We can sit back and know that we've done what we can do. Now God's going to do what he can do."

Water already has forced hundreds of residents in the Fargo area from their homes and submerged basements and yards in an untold number of houses along the river. Emergency crews in boats had to rescue about 150 people from their homes in neighboring communities in Minnesota, where about 20 percent of households in Moorhead had been urged to leave.

National Weather Service forecasters say the river is retreating because cold weather - just 17 degrees at 7 a.m. today - has been freezing water that normally would be flowing into the river. By the time that water melts, the biggest flooding threat should have passed, Hudson said.

Volunteers have been asked to inspect the levees for problems, joining National Guard inspection teams. The task is monumental, with more than 35 miles of levees around Fargo.

"I don't think there's an inch of riverfront on the Fargo side that doesn't have some kind of levee," said city engineer Mark Bittner. "We encourage neighborhoods to get together and have their own dike patrols and assist us."