The crash of the two drones has triggered federal investigations and renewed doubts about the safety of Amazon's ambitious delivery program.

In the United States, Amazon is facing a new crisis for its drone delivery program. Two Prime Air aircraft crashed Wednesday in Tolleson, near Phoenix, after colliding with a construction crane, CNBC reported. The crash, which did not cause any serious injuries but required treatment for one person for suspected smoke inhalation, led the company to temporarily suspend its service in the area.

According to local police, the two drones (model MK30) were flying in the same direction when they struck the boom of a crane in a commercial area, close to a warehouse of the e-commerce giant. The heavily damaged drones ended up in the backyard of a neighboring building.

Federal investigations already opened

The Federal Aviation Administration (FAA) and the National Transportation Safety Board (NTSB) immediately launched investigations. Initial official reports describe "substantial damage" to the drones. Amazon confirmed that it is in contact with authorities and cooperating with the investigation.

This isn't the first time Prime Air has been in the spotlight. Last January, Amazon had to temporarily halt drone deliveries in Tolleson and College Station, Texas, after two crashes at its Pendleton, Oregon, testing site. According to CNBC, the company blamed the failures on a software glitch and announced in March that it was gradually resuming operations after claiming to have fixed the flaws.

A technology still in doubt

Amazon is touting the presence of a so-called "detect and avoid" system, which is supposed to allow drones to identify obstacles in flight and on the ground in order to avoid them. This device is also presented as a guarantee that allows the machines to travel long distances without direct human supervision. But the Tolleson accident shows that, despite these technological promises, the safety of the device is questionable.

For more than a decade, Amazon has been trying to bring to life founder Jeff Bezos's vision: delivering everyday products, from toothpaste to batteries, in less than 30 minutes using autonomous drones. Yet, after a decade of massive investment and optimistic marketing, Prime Air remains limited to a select number of American cities. Officially, the company has set a monumental goal: to reach 500 million annual drone deliveries by 2030.