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FILE -- Lt. Jeff Loman is on administrative leave while the Oakland Police Department probes allegations he allowed his girlfriend to drive a police vehicle that was involved in a wreck in Napa County, according to sources. (Alison Yin/Staff)

OAKLAND -- A former deputy police chief demoted to lieutenant after a sexual harassment investigation is on administrative leave while the department probes allegations he allowed his girlfriend to drive a police vehicle that was involved in a wreck in Napa County, police and other sources confirmed Monday.

Police sources confirmed that Lt. Jeff Loman is under investigation by the Internal Affairs Division for possible policy violations. Authorities identified the woman driving the car as Priscilla Yambao, a civilian employee of the department.

The internal probe began last week after the California Highway Patrol notified Oakland police they were investigating a collision involving an unmarked Oakland police car driven by Yambao and another car about 4:30 p.m. Oct. 7 on Bucks Canyon Road in unincorporated Napa County.

The CHP said Monday that a black Ford Crown Victoria driven by Yambao crossed a double line and collided head-on with a Honda. The Honda driver was hospitalized with minor injuries. Yambao was also injured but sought her own medical aid, the CHP said. Neither driver had been drinking and the crash is still under investigation, the CHP said.

No one else was in either of the vehicles.

Loman, who sources said was off duty when the accident happened, was placed on administrative leave Friday. It was not known Monday if Yambao is under internal investigation.

Loman's current assignment is patrol division watch commander in East Oakland. Watch commanders are usually not allowed to take police vehicles home with them either at night or on their days off, but Loman apparently had, police officials said.

Loman's attorney, Alison Berry Wilkinson, acknowledged Monday that Loman was being investigated and that she is awaiting full details of what happened. "It is hoped that the department will conduct a full, fair and complete investigation because things are not always as they seem when allegations are initially made," she said.

Loman was demoted in May 2009 after he was investigated for allegations of sexual harassment, divulging confidential information and untruthfulness. It was never confirmed which allegations were sustained by internal investigators. Usually, if one instance of untruthfulness is found, the officer is fired.

That investigation resulted from a complaint filed in November 2008 by a female sergeant, who later was promoted to lieutenant. She had said she'd become uncomfortable when Loman discussed meeting her for dinner to talk about a possible promotion.

Loman was believed to be the highest-ranking officer in department history to be demoted because of a disciplinary matter.

Before becoming a deputy chief in early 2008, Loman had been a captain commanding the Criminal Investigation Division.

He had been a K-9 handler as an officer and, as a sergeant, a homicide investigator.