Authorities in south Texas are searching for a pickup truck driver who peeled away from a traffic stop on Sunday -- with a police officer hanging from the driver's side window.

The Weslaco Police Department said in a Facebook post the incident unfolded after officers received a report of a man who was asleep behind the wheel of a pickup truck that had the engine still running.

When officers confronted the man -- identified by police as 28-year-old Adan Loa -- he refused to turn off the truck and fled the scene.

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"In his attempt to flee he struck a patrol unit and also injured a Weslaco Police Department Officer," police said.

The officer was injured after Adan Loa drove off with the cop hanging on the truck door. (Weslaco Police Department)

The officer who was struck by Loa was not seriously injured, according to Weslaco Chief Joel Rivera

Authorities are searching for Adan Loa, who has active warrants and drove off with an officer still hanging on the side of his truck. (Weslaco Police Department)

"That officer did sustain bruising to his person and he's been cleared and he's back on the job as of today," Rivera told CBS4 on Monday.

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Loa has active warrants for burglary of a habitation, assault family violence and evading arrest, officials said.

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Authorities are asking anyone with information on Loa's whereabouts to contact Weslaco Crime Stoppers at 956-968-8477.