Google says three of its self-driving vehicles were involved in crashes in the Phoenix, Ariz. metro area in August.

The California-based company says its drivers were manually controlling the vehicles during two of the accidents, but the third was operating in the autonomous mode when it was rear-ended, reported The Arizona Republic.

Google began testing an unknown number of self-driving Lexus SUVs in Chandler in August. The company did not say how the accident rate compares to testing in other cities.

Google has tested its autonomous vehicles in Mountain View, California; Austin, Texas; and Kirkland, Washington. They extended the testing to Arizona to see how the cars would respond to things such as dust storms and golf-cart crossings, according to Google officials, and focused on Chandler because of its technology industry.

A self-driving Google Lexus was rear-ended in Chandler while stopped at an intersection on Aug. 22. There were no injuries.

On Aug. 16, a Google vehicle being driven manually at 42 mph was rear-ended by a car traveling at 67 mph. The 25-year-old driver of the second vehicle was arrested on suspicion of DUI, said Chandler police spokesman Sgt. Daniel Mejia.

A passenger in the Google vehicle was treated for a concussion, according to the police report.

A Google driver was cited in an Aug. 9 crash, but the company says its data shows that the other driver actually ran a red light and hit the Google vehicle during a left turn.