Capt. Cy Vierra said police brought their findings to the district attorney's office for review and it was decided "there was nothing criminal to
"The investigation is completely over unless new information comes to light," said Vierra, commander of the Youth and Family Services Section.
It was the second time the same conclusion had been reached by the authorities. Last week, after reviewing interviews with the student, who denied anything inappropriate took place, the district attorney's office decided not to file charges.
But Vierra decided to have investigators find and interview the people who had first brought their concerns about the relationship to the school district. He said it was a parent and another student.
Vierra would not say what the two considered inappropriate conduct. But based on the police investigation, he said, "It was not criminal."
Police did not interview Dobbins. Because investigators found no evidence of a crime, "there was no reason to talk to him."
The Oakland school district is also looking into Dobbins's conduct.
"The matter is still in discussion, and the district is reviewing all available evidence with appropriate haste, but we also want to be thorough," said Troy Flint, the district spokesman. "There's no rush to judgment here."
Staff writer Katy Murphy contributed to this story.