Agents assigned to the RGV Marine Unit in the Rio Grande Valley (RGV) sector said that at around 2:25 am they saw four people on the Fronton Main Landing near Fronton, Texas, shoot more than 50 rounds at their patrol boat using automatic weapons.
No agents were injured, but Customs and Border Protection sources told Fox News the "vessel was hit several times."
CBP has launched an investigation, saying that the Mexican nationals responsible for the shooting have yet to be identified.
The river Rio Grande, which flows from the southwest of the United States into parts of northern Mexico, forms part of the US southern border with Mexico. The region, which is relatively easy to cross, is known to be a hotbed for illegal-immigrant apprehensions, with 36,872 migrants apprehended in July, according to CBP data.