PRESIDIO, Texas—Helicopters dropped massive 3,000-pound sandbags as work by a prison crew to create a makeshift dam resumed Saturday in this rural border city that remains threatened with flooding from the Rio Grande.

As rains had continued to fall in Mexico, Presidio authorities feared Saturday morning their Mexican counterparts would be forced to release more water from the Luis Leon Reservoir.

But on Saturday afternoon, Chihuahua state Civil Protection Director Issac Olivas said the water level at the reservoir is dropping so they’ll be able to release less water than they had been releasing earlier this week. Numerous levee breaks in Mexico has contributed to flooding south of the border but eased some of the pressure on the U.S. levees, where river levels were holding steady said Rod Ponton, the Presidio County Attorney.

Ponton said they will continue to build the dam and try to shore up a weakened levee. Workers Saturday were preparing to line a section of the levee with heavy plastic anchored by sandbags to keep water from leaking through. About 10,000 small sandbags were to anchor the plastic, Ponton said.

The Rio Grande in Presidio, a dusty border city of nearly 5,000 about 250 miles southeast of El Paso, has been under threat of massive flooding for nearly two weeks. The river has been rising thanks to torrential rains in Mexico and the forced release of water from the Luis Leon Reservoir. That water flows into the Rio Conchos, which feeds the Rio Grande in this part of the border.

Earlier this week, a small levee break several miles east of the populated areas of the city caused floodwaters to wash over an 18-hole golf course and envelop hundreds of acres of farmland.

Efforts that started Thursday night to construct a makeshift dam along a railroad track that abuts the levee at the eastern edge of Presidio continued Saturday. A prison crew of about 150 worked on the dam in an attempt to keep the water from swamping low-lying areas of the city.