SAN LEANDRO — A 26-year-old man was arrested Sunday on suspicion of molesting a 9-year-old girl aboard a BART train, officials said Monday.

Police said about 3:41 p.m. Sunday the girl was seated on a San Francisco-bound train when a man sat next to her and began to touch her on the leg and buttocks.

A family member of the girl intervened and they got off at the Bay Fair Station and called police.

The suspect, identified as Marcus Brown, stayed on the train. BART police boarded the train at the Coliseum station, detained Brown and located another witness to what had happened, police said.

The girl was brought to the Coliseum Station where she identified Brown as the assailant, police said.

Brown was questioned by detectives before being arrested on suspicion of sexual battery and annoying or molesting a child. He was also issued a prohibition order that forbids him from riding BART for up to a year, officials said.

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