CHICAGO (WLS) -- A woman was robbed of her cell phone on the CTA's Red Line subway in the Loop Thursday night, Chicago police said.The robbery occurred on a Red Line train at about 11:30 p.m. in the first block of South State Street, police said. The 24-year-old victim told police that four men approached her and snatched her phone.One suspect was arrested after exiting at the Monroe stop and two others continued on the train to the Chinatown stop where they were taken into custody, police said.Police said charges are pending.There have been a number of robberies on the Red Line in recent days, including a pregnant woman who said she was attacked and robbed by a group of teenagers last weekend.Twenty-eight-year-old Juatonna Davis who is four weeks pregnant, says it happened as she and her friend got off at the Roosevelt station.The teens began blocking Davis and her friend from getting off the train."I feel people kicking me, going through my pockets, they attacked us," said Davis. "The whole time my friend was yelling, 'She's pregnant, she's pregnant, don't fight her, she's pregnant!'"The violent encounter came just hours before two men were beaten and robbed by a group of teenagers on the Red Line at State Street Sunday night.Another violent attack was reported last week on a Red Line train near the Harrison stop. Police said a 37-year-old man was on the train when he was punched in the face and robbed.It's not clear if any of incidents are related, but Chicago police have stepped up patrols near CTA Red Line stops.