A Mexican military helicopter fired two shots on U.S. Border Patrol agents early Thursday morning after crossing into American airspace, though no injuries or damages were reported.

The helicopter flew about 100 yards into Arizona while on a “drug interdiction operation” near the border, U.S. border officials said, according to KVOA

The incident happened sometime between midnight and 6 a.m. Thursday morning on the Tohono O'odham Indian Nation reservation in southern Arizona, border officials in nearby Tucson said. 

It “apparently involved an army helicopter,” a Mexico federal prosecutor spokesman told Reuters. The helicopter returned to Mexico, which apologized to U.S. authorities, KVOA reported. The incident is under investigation.

Border security has been at the forefront of debate recently as a flood of children illegally cross into the U.S. to escape violence. Republicans and Democrats have parried over how to deal with the crisis. Earlier this week, Arizona Gov. Jan Brewer (R) criticized the federal government for not securing the border to prevent such crossings, and Texas Gov. Rick Perry (R) invited President Obama to visit the Texas border. 

Homeland Security Secretary Jeh Johnson said Wednesday that unaccompanied children who illegally migrated to the U.S. have “no free pass” to stay.