(CNN) -- The FBI has launched an investigation into a Sunday shooting involving a sports utility vehicle that was fired upon by U.S. Customs and Border Protection, in what agents called a "significant incident" at the Texas-Mexico border.
Border patrol officers fired at the SUV after it was involved in an accident in El Paso, Texas, about 1 a.m. Sunday, then fled the scene and headed toward the Zaragoza International Bridge, FBI spokeswoman Marths Terrazas told CNN.
"There were gunshots fired at the vehicle by [CPB] officers. I don't know about any fire back from the vehicle," Terrazas said. "It fled into Mexico and went past the [point of entry]."
Terrazas said despite reports that the same SUV was spotted later at a predawn shootout Sunday in Ciudad Juarez, Mexico, there was no known connection between the SUV and the Juarez shooting, Terrazas emphasized.
"I want it known that its two separate incidents," Terrazas said in a telephone interview. "This is significant because it's not a common occurrence. I think that's why it's become even more important for us to cover it correctly."
A predawn, hour-long gun battle -- the latest volley in an escalating series of attacks on Mexican federal police by drug cartel hitmen -- left three cartel gunmen dead Sunday in Ciudad Juarez, according to a Mexican federal police spokesman.
Assaults against federal police have increased in recent months since they took full control of security in the city from the Mexican military on April 9.