Police are asking BART riders who have had cellphones stolen recently to come forward after two boys, ages 14 and 17, were arrested July 18 on robbery charges.

The teens allegedly grabbed an iPhone from a BART passenger at the Balboa Park station and fled. The victim and two other people gave chase, but one of the helpers was pepper-sprayed by one of the youths, police said. However, with the help of a third person, San Francisco police officers were able to catch the teens.

BART reported that the youths are suspected of other thefts at the Balboa Park station, along with incidents at the Glen Park, 16th Street and 24th Street stations.

Police said the boys would enter trains and walk down the aisle looking for victims. They would sit separately but within sight of each other. After finding a victim, one suspect would give the other a signal, grab the cellphone, then flee.

The suspects are being charged with grand theft and conspiracy to commit a crime, among other offenses. Call BART police at (510) 464-7040 if you have any information.