PEMBINA, N.D.

Volunteers worked 24 hours a day through Thursday to raise the ring dike around Pembina to 58 feet as the Red River of the North inched upward toward the 55-foot level.

The massive effort brought new hope to North Dakota’s oldest community that people could stave off major flooding, even as rising water has left it a virtual island.

‘‘We’re going to make it,’’ Pembina Mayor Hetty Walker said Thursday afternoon.

The Red River is expected to crest at 58 feet in Pembina, either Sunday or Monday, according to the latest National Weather Service forecast. By 1 p.m. Thursday, it stood at 54.5 feet.

Flood-fighting efforts were hampered by a lack of access to town. The Pembina River, which flows into the Red at Pembina, continued to back up, spilling more than 18 inches of fast-moving water across Interstate 29 by early Thursday afternoon.

Hundreds of volunteers arriving to help with sandbagging efforts had to be ferried into town via HEMTTs, 10-ton National Guard cargo trucks. Except for sandbag trucks, the highway was closed .

Pembina, with a population of about 650, has been under a mandatory evacuation since Tuesday evening.

People registered to help with the flood-fighting effort can stay overnight. That number totaled about 70 Wednesday night.