Mexico will assist American authorities investigating a June 5 a shooting attack on a U.S. Customs and Border Protection helicopter, the country's Foreign Relations Department said on Thursday, according to the Associated Press.

The aircraft, which was apparently unarmed, was forced to make an emergency landing in Laredo, Texas, after bullets hit its side and rotor blade; no one was harmed in the incident. The chopper had been flying over an area notorious for illegal border crossings and drug smuggling, CNN noted.

The FBI noted that the helicopter was struck several times by gunfire about 5 p.m. during a flight near the Rio Grande.

"The rounds penetrated and damaged the aircraft, forcing the pilot to make an emergency landing," investigators detailed. "The pilot sustained no injuries, and no individuals on the ground were affected," their statement added.

Laredo Police noted that preliminary indications suggested that the gunfire came from the Mexican side of the border; in general, incidents of cross-border shootings are rare, though, police spokesman Joe Baeza added.

The Mexican government, while offering its assistance in the investigation, insisted that it "categorically rejects any attempt to see the border as a security threat," according to the AP. It has has long opposed any militarization of the border, the newswire explained.

The Foreign Relations Department noted that U.S. Customs and Border Protection had contacted the Mexican Embassy in Washington to inform neighboring authorities that two more UH-60 Blackhawk helicopters were being sent to the border and that their mission in the area was to transport personnel as part of an "exclusively civil purpose," Crónica reported.

Democratic U.S. Rep. Henry Cuellar, who represents Laredo, told the Brownsville Herald that the choppers were expected to arrive on Friday and would be charged with patrolling the Rio Grande from Laredo to the Lower Rio Grande Valley.

"I understand the argument about militarization," Cuellar said. "I don't want to militarize the border, but we are using these helicopters for the armor so they can stop those types of bullets."

Unnamed officials, meanwhile, told the newspaper that the helicopters' pilots will be armed and could shoot back if they were to again come under fire.