Fargo, N.D. ? Officials ordered the evacuation of one Fargo neighborhood and a nursing home late Thursday after authorities found cracks in an earthen levee built to protect the area from the threat of the rising Red River.

Residents were not in immediate danger, and floodwaters were not flowing over the levee, Mayor Dennis Walaker said Thursday night. The evacuation was being enforced as a precaution.

Officers were going door to door to the roughly 40 homes in the River Vili neighborhood and were evacuating Riverview Estates nursing home. Authorities also called for the voluntary evacuation of about 1,000 people who live between the main dikes and backups in various parts of the city. That evacuation could become mandatory, officials said.

Authorities across the river in Moorhead, Minn., also stepped up evacuations Thursday. They recommended that residents leave the southwest corner of the city and a low-lying township to the north.

Fargo residents have been scrambling in subfreezing temperatures to pile sandbags along the Red River. They spent much of Thursday preparing for a record crest of 41 feet — only to have forecasters add up to 2 feet to their estimate.

The first estimate sparked urgency among thousands of volunteers in Fargo, but the second sparked doubts about whether a 43-foot-high wall of water could be stopped. In Moorhead, City Manager Michael Redlinger said portions of his city’s dike could not be easily raised to withstand a 42-foot crest.

“Now everything’s up in the air,” he said.

The old estimate was 41 feet by Saturday afternoon, and thousands of volunteers had labored throughout the day to raise the dikes around North Dakota’s largest city to 43 feet. City and emergency officials had said they were confident the city would make it, but will now have to build higher.

The National Weather Service said late Thursday afternoon that the Red was expected to crest between 41 and 42 feet, but could reach 43 feet. It said water levels could remain high for up to a week — a lengthy test of on-the-fly flood control.

“Record flows upstream of Fargo have produced unprecedented conditions” on the river, which “is expected to behave in ways never previously observed,” the weather service said.

Tim Corwin, 55, whose south Fargo home was sheltered by sandbags to 43 feet, said he wasn’t giving up but was pessimistic after hearing the new potential crest.

“I’ve lived here 40 years and over a 30-minute span I’ve reached a point where I’m preparing to evacuate and expect never to sleep in my house again,” he said.

The city of 92,000 unveiled a contingency evacuation plan Thursday afternoon, but at least four nursing homes already had begun moving residents by then.

“A few of them said they didn’t want to go. I said I’m going where the crowd goes,” said 98-year-old Margaret “Dolly” Beaucage, who clasped rosary beads as she waited to leave Elim Care Center.

“I’m a swimmer,” she said, smiling, “but not that good a swimmer.”