Mexican authorities have placed alligator warning signs from one side of Reynosa to the other.
Officials told Action 4 News that sightings prompted them to place 10 warning signs have been placed along the Rio Grande.
The signs were placed on the Mexican side of the river from the Hidalgo-Reynosa International Bridge to the Anzalduas Dam.
Authorities are concerned that the large reptiles can come into contact with undocumented immigrants or area residents visiting recreation areas along the river.
A sign at Anzalduas Park on the Texas side of the Rio Grande south of Mission prohibits swimming but there are no signs warning against the presence of alligators.
Watch our video clip to watch interviews with Mexican officials and residents who claim to have seen alligators in the Rio Grande.