PLEASANTON -- A 15-year-old girl who disappeared more than a week ago and was thought to be with a man twice her age was found Monday night in Pleasanton, police said Tuesday.

Pleasanton police did not return calls and emails for comment and it was not known where the girl was found Monday night. She was not injured and was released to her mother, said Fremont police spokeswoman Geneva Bosques.

The teenager was reported missing May 5 from her uncle's home in the Irvington district of Fremont. A preliminary investigation shows the teen left her uncle's home voluntarily and was not held against her will, Bosques said.

Police believe she was with 30-year-old Ryan Griggs, who may still be driving a stolen white Ford F150 pickup with a white camper shell. The truck's California license plate is 6E82209.

Police have not said if investigators believe there had been sexual activity between the two. Based on that possibility, this newspaper is not publishing her name.

Staff writer Kristin J. Bender contributed to this report. Contact Natalie Neysa Alund at 510-293-2469. Follow her at Twitter.com/nataliealund.