LAREDO, Texas - Experts say drenching storms have raised reservoirs along the U.S.-Mexico border to their highest levels in decades.

With yet another storm on the way, Laredo officials have made calls to 3,000 homes, urging residents to leave before the Rio Grande crests there. City spokeswoman Xochitl Mora said a shelter will be opened at the civic center, and residents in low-lying areas are being asked to move before the river crests in downtown late Thursday.

Officials evacuated the flood-threatened Vega Verde subdivision in Del Rio, Texas, some 110 miles upstream from Laredo.

High waters in the northern Mexican state of Coahuila have already damaged some 10,000 homes, many of which were swamped in waist-deep water. To the southeast, Mexican officials evacuated nearly 18,000 people from houses in Ciudad Anahuac.

The rain-swollen river and water releases from the International Amistad Reservoir upstream won't allow the storm runoff system to drain properly. Laredo officials have closed two international bridges as the Rio Grande swells from the remnants of Hurricane Alex and releases from reservoirs upstream.

Bridge One, the international bridge connecting the downtowns of Laredo and Nuevo Laredo, Mexico, was closed at noon to give workers time to remove heavy steel shade canopies from the bridge before the expected crest on Thursday. The water is expected to rise to 38.5 feet, which is high enough to touch but not run over the bridge.

The Colombia Bridge, which connects the city's northwestern edge to Nuevo Leon, closed at 6 p.m. Wednesday evening.

Both bridges could be topped by the swollen Rio Grande Thursday.

Two other bridges, including the busy commercial World Trade International Bridge, should remain open.

According to the International Boundary and Water Commission, water behind the binational Amistad Dam on the Rio Grande was at its highest level since 1974, forcing a release at the fastest rate in a quarter century.