(CNN) -- Two international bridges between Nuevo Laredo, Mexico, and Laredo, Texas, were closed Wednesday because of rising water on the Rio Grande, Laredo officials said.
Laredo's International Bridge I is one of four that connect the two cities, but because it has the lowest elevation it was closed, said Laredo spokeswoman Xochitl Mora Garcia.
Officials are worried that the high water may damage the bridge and are removing steel canopy shades authorities believe add weight and stress to the span, the spokeswoman told CNN.
Officials expect the bridge to be closed for at least three days, Mora Garcia said.
The Rio Grande, which usually has a depth of 6 to 10 feet at Laredo, is expected to crest Thursday at nearly 39 feet, the spokeswoman said.
A second crossing, the Colombia Bridge, was closed because the water is cresting there at a higher level, Mora Garcia said. The bridge will be closed until further notice.
It will take about a day to remove the canopies at International Bridge I and another day to reinstall them after the high waters subside, Mora Garcia said.
About 10,000 to 12,000 pedestrians and 12,000 to 14,000 noncommercial vehicles cross International Bridge I each day, Mora Garcia said.
Laredo has a population of about 250,000, but that typically swells to 350,000 to 400,000 as Mexicans come to the city to shop, visit family or engage in recreational activities, the spokeswoman said. The city is the nation's No. 1 inland port, Mora Garcia said.
International Bridge II and the World Trade Bridge will remain open. Laredo owns and operates the four bridges, Mora Garcia said.
"Pedestrians who have no other alternative to reach Nuevo Laredo are encouraged to return immediately or make arrangements to travel by vehicle by Bridge II," the city said in a news release. "Bridge II will NOT accept pedestrians to return to Nuevo Laredo. Colombia Bridge and World Trade Bridge can accept pedestrians."
In addition, buses from Nuevo Laredo will be transporting would-be pedestrians back and forth over Bridge II over the vehicle-only bridge. The arrangement was made between U.S. and Mexican officials and will remain in effect for the duration of the emergency situation, Mora Garcia said.
Laredo was planning to open its emergency operation center Wednesday afternoon. Residents in the 100-year floodplain will be notified to evacuate if necessary, officials said.
The Laredo Civic Center can be converted into a shelter, the city said.
On Wednesday, Texas Gov. Rick Perry announced that he was sending vehicles, guardsmen, and rescue divers to the Laredo area.
"As South Texas continues to feel the effects of Hurricane Alex, we are closely monitoring a storm system that is expected to bring more heavy rains to the area and increase flooding along the Rio Grande," Perry said.
Water service in Laredo will not be affected, but residents in Nuevo Laredo may have water service at 50 percent of the city's operating capacity, Laredo officials said.
Communities throughout northeastern Mexico have been flooded as a result of heavy rains spawned by Hurricane Alex nearly two weeks ago.
In the city of Reynosa in Tamaulipas state, on the border with Texas, 23,000 people were in danger Wednesday because of flooding by the Rio Bravo, the government-run Notimex news agency said.
Alex stormed onshore as a Category 2 Hurricane on June 30, causing at least six deaths in Nuevo Leon state.