Amazon is facing federal probes after two of its Prime Air delivery drones collided with a crane in Arizona, prompting the company to temporarily pause drone service in the area.

The incident occurred on Wednesday around 1 p.m. EST in Tolleson, Arizona, a city west of Phoenix. Two MK30 drones crashed into the boom of a stationary construction crane that was in a commercial area just a few miles away from an Amazon warehouse. No injuries were reported.

“We’re aware of an incident involving two Prime Air drones in Tolleson, Arizona,” Amazon spokesperson Terrence Clark said in a statement. “We’re currently working with the relevant authorities to investigate.”

Both drones sustained “substantial” damage from the collision on Wednesday, which occurred when the aircraft were mid-route, according to preliminary FAA crash reports.

The Federal Aviation Administration and National Transportation Safety Board are investigating the incident. The NTSB didn’t immediately respond to a request for comment.

The probes come just a few months after Amazon, in January, paused drone deliveries in Tolleson and College Station, Texas, temporarily following two crashes at its Pendleton, Oregon, test site. Those crashes also prompted investigations by the FAA and NTSB. The company resumed deliveries in March after it said it had resolved issues with the drone’s software, CNBC previously reported.

For over a decade, Amazon has been working to bring to life founder Jeff Bezos’ vision of drones whizzing toothpaste, books and batteries to customers’ doorsteps in 30 minutes or less. But progress has been slow, as Prime Air has only been made available in a handful of U.S. cities.

Amazon has set a goal to deliver 500 million packages by drone per year by the end of the decade.

Tolleson police and fire departments didn’t respond to a request for comment about the Wednesday incident.