The Santa Maria California Highway Patrol officer who was arrested in Arroyo Grande on Aug. 8 on suspicion of driving under the influence of drugs was found to have a prescription sleep aid in his system, according to the San Luis Obispo County District Attorney's office.

Michael Shane Mallory, 37, of Arroyo Grande was arrested after he crashed his 2004 Ford Explorer into two parked cars in his neighborhood while turning a corner on his morning commute to work, police said. No injuries were reported.

When police responded to the crash, officers said Mallory seemed impaired, and they conducted a field sobriety test. The test eliminated alcohol as a factor.

Upon further investigation, blood tests released this week showed that Mallory had taken Zolpidem, a generic version of the prescription drug Ambien, according to the District Attorney's office.

The blood tests were negative for alcohol and standard illegal drugs such as methamphetamine, heroin and marijuana, officials said.

The District Attorney's office is currently evaluating the results of the tests to determine how to proceed with the case. Among those plans is to contact a drug expert to determine at what level Zolpidem could cause impaired driving. The amount of the drug found in Mallory’s blood tests was not released.