A flock of drones above Coors Field earlier this month has sent federal law enforcement on a chase to track down the operators.

More than a half dozen drones were spotted above the stadium on April 3-5 during the Rockies’ first home series against the Phillies.

No one has been arrested, but the drone pilots could still face a later fine.

Both the FBI and the Federal Aviation Administration issued a warning on Thursday in an attempt to keep drones away from Coors Field in the future because of the potential threat they pose.

“The illegal drone activity did not jeopardize anyone’s safety, but there were enough violations that the teams on the ground were concerned about the number of operators that did not seem to understand the seriousness of the situation. Thus the proactive messaging,” FBI spokesperson Vikki Migoya said in a statement.

The airspace directly surrounding stadiums is often restricted by the FAA to ensure the crowd’s safety and that games can be played without any interruptions.

The United States government has shifted a focus on drone defenses at sporting events with heightened fears of them causing potential terror attacks, with $500 million being invested for security at World Cup host cities for this summer.

Regardless of imminent threats, however, Migoya said the problem is that any illegal drone activity is a distraction for law enforcement.

“Every instance of illegal drone activity requires a law enforcement intervention to ensure the intent is not nefarious; the fewer violations there are, the more law enforcement can focus on what might be a true threat,” she said.

Coors Field has a restricted airspace within 3 miles of the stadium starting one hour before and concluding one hour after games, with pilots responsible for checking the guidelines before they fly.

Drone operators who violate those restrictions could face fines up to $75,000 and lose their licenses, the FAA said.