CHICAGO (STMW) — Two days after warning the public about the theft of electronic devices on Green Line trains, police arrested four suspects Thursday, the youngest being a 10-year-old boy.

On Tuesday, Harrison Area detectives issued community alerts about the robberies on the trains on the West Side. And after CTA Security provided surveillance footage of the crimes, police set up a sting operation.

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Officers from the Wood and Harrison districts went undercover and about 9:56 a.m. Thursday, saw three boys fleeing from a CTA platform, a release from police said.

The juveniles — ages 10, 13 and 14 — had just been involved in a strong-armed robbery in which a victim, seated on a Green Line train, had his mobile phone forcibly snatched from his hand, the release said.

After a brief foot pursuit, the three were apprehended and positively identified by the victim.

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Later Thursday, at about 6:40 p.m., Harrison District officers on a similar sting were standing at the bottom of the exit stairs at the Green Line Pulaski Station when they were alerted by a female victim that her phone had been taken.

Almost immediately, the 15-year-old offender ran down the exit stairs, directly into police officers, the release said. He was taken into custody and the victim’s phone recovered.

All four boys were charged as juveniles with strong-armed robbery.

The investigation into previous Green Line robberies continues, according to police.

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(Source: Sun-Times Media Wire © Chicago Sun-Times 2010. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)