A Mexican law enforcement helicopter crossed over into U.S. airspace early Thursday and opened fire near U.S. Border Patrol agents.

The incident occurred around 5 a.m. in southern Arizona, about 100 yards north of the U.S.-Mexico border. Mexican authorities were tracking and trying to apprehend about 45 people in a drug operation as the subjects were attempting to cross into the United States, the Los Angeles Times reports.

A couple of shots were fired into Arizona on the Tohono O'odham Reservation, near the town of San Miguel, Arizona, according to a statement from Customs and Border Protection. Fortunately, nobody was injured.

"At approximately 5:45 a.m. Thursday morning, a Mexican law enforcement helicopter crossed approximately 100 yards north into Arizona nearly 8 miles southwest of the Village of San Miguel on the Tohono O'odham Indian Nation while on a law enforcement operation near the border," Border Patrol spokesman Peter B. Bidegain III wrote in an email, according to Time. "Two shots were fired from the helicopter but no injuries or damage to U.S. property were reported. The incident is currently under investigation."

U.S. officials said in a statement that Mexican authorities said the shots were a "mistake." Border Patrol Tucson Sector union president Art del Cueto said Mexico quickly contacted U.S. authorities to apologize for the incident.

The last 10 years have seen more than 300 border incursions by Mexican military and law enforcement authorities, according to data released recently by Rep. Duncan Hunter, R-Calif., reports AZ Central.

In January, two armed Mexican soldiers crossed into the same part of Arizona and drew their weapons on Border Patrol officers there. No one was injured in that incident either.