OAKLAND (CBS SF) — The cause of a vehicle collision involving Oakland Mayor Jean Quan last month in West Oakland remains under investigation and cellphone use by either driver involved in the collision has not been ruled out, police said Tuesday.

Oakland police spokeswoman Officer Johnna Watson said Tuesday night that the police department’s Friday statement, which ruled out cellphone use as a cause of the collision, was not accurate.

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Watson said the department’s Traffic Investigations Unit was not able to determine whether or not cellphones were being used at the time of the crash.

The collision occurred shortly after 5:30 p.m. on June 8 near the intersection of 26th and Market streets in West Oakland.

Quan told reporters at the time that she was driving between two community events when another vehicle struck the left rear tire of her car.

Police said Friday in a statement that an investigation had found the primary factor in the collision was a failure to stop at a red light signal.

“The driver most at fault for the collision was unable to be determined due to conflicting accounts,” the statement said.

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Quan pointed to the police report as support for her statements to reporters after the collision that she had not been using her cellphone while driving.

“I stand by my original statement that I do not believe I ran the red light,” Quan said in a statement, noting that there were no witnesses to the actual collision.

“The damage to the car reveals that I was hit from behind; the impact spun my vehicle around and flattened my left rear tire,” Quan said.

Quan, who is facing 16 opponents in her re-election bid in the November election, submitted her cellphone records to Oakland police to confirm her assertion that she was not on her phone at the time of the collision.

Quan’s driving came under question previously when two Oakland residents submitted photos to a local television station showing her using her cellphone without a hands-free device while driving.

Quan also acknowledged in June that she was cited for a “rolling stop” while going through an intersection in Fremont in April 2013.

The cause of the collision remains under investigation.

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