New details on Heather Locklear's arrest are emerging, including a 911 call and the battery of tests the actress underwent Saturday evening.

A spokesperson for the California Highway Patrol confirmed to ET a 911 call was made by a concerned citizen around 4:30 PM Saturday after she observed a woman acting strangely and driving erratically as she left a parking lot in Montecito, California- an upscale town adjacent to Santa Barbara.

Among the details, the CHP rep tells ET Locklear was observed by the citizen as backing over a pair of sunglasses several times while she was attempting to maneuver out of the parking area.

The citizen observed her leaving and became concerned when they say they spotted the actress stop on East Valley Road, exit her vehicle and stumble into the traffic lane.

When an officer arrived, Locklear was seated alone in the driver's seat and was stopped in a travel lane. A CHP officer asked for her license, registration and proof of insurance and identified her as Heather Locklear.

According to the police report, Locklear appeared to be disoriented and after an on-scene evaluation, a DUI investigation was initiated and although impairment was exhibited during the tests, alcohol was ruled out as a factor.

Locklear was booked at 7 p.m. Saturday on suspicion of driving under the influence of a controlled substance and was later released from custody.

Locklear left a treatment facility in Arizona in July after receiving four weeks of treatment for anxiety and depression. Sources tell ET she's recently been attending AA meetings in Malibu.

Representatives for Locklear decline to comment but have referred ET to Locklear's attorney.