The timeline for Amazon’s flying delivery service has been pushed back after one drone caused a brush fire.

Jeff Bezos, Amazon founder and CEO, has long been vocal about his plan for creating a fleet of drones to deliver Prime packages in 30 minutes.

However, despite spending more than $2 billion on the project, Amazon is still not in a place to launch the planned delivery system.

In fact, a Bloomberg investigation found that the service is plagued by technical challenges and safety concerns.

Furthermore, drones have crashed in test runs, and have even been the cause of a brush fire that spanned 25 acres.

Reports found that last year, five delivery drones crashed at Amazon’s test site in Oregon, with one causing the fire.

That specific drone malfunctioned while in mid-air, leading to its motor shutting off.

It then turned upside down and plummeted around 160 feet to the ground, sparking a fire that had to be put out by the local fire department.

It’s expected for experimental aircraft to malfunction, however, some Amazon employees told Bloomberg that the company was taking “unnecessary risks” to get the program up and running.

“With rigorous testing like this, we expect these types of events to occur, and we apply the learnings from each flight towards improving safety,” Amazon spokesman Av Zammit said in an emailed statement.

“No one has ever been injured or harmed as a result of these flights, and each test is done in compliance with all applicable regulations.”

Despite the risks and setbacks, Amazon still plans to ramp up testing in the coming months, Bloomberg reported.  

The company has set a goal of conducting 12,000 tests for 2022.

However, as of late February, fewer than 200 had been completed.

Amazon also wants to add two new testing locations this year in College Station, Texas, and Lockeford, California.

Most recently, Alphabet Inc.’s Google Wing kicked off its own drone testing program.

Similarly, Walmart and United Parcel Service (UPS) are developing their own drone delivery systems.

This article originally appeared on The Sun and was reproduced here with permission.