CHICAGO (CBS) — Two teenage girls have been charged with beating and robbing a pregnant woman on a CTA Red Line train last week.

The 15-year-old and 16-year-old girls turned themselves in on Saturday, after seeing surveillance images of themselves on the news and on social media.

They have been charged with robbery and aggravated battery, and were due to appear in Juvenile Court on Monday.

On Friday, Chicago Police released surveillance images of six people wanted for attacking a pregnant woman and her friend on a Red Line train near the Roosevelt stop on Dec. 29.

The group got into an argument with a pregnant 28-year-old woman shortly before 7 p.m., and one person in the group hit her in the back of the head, knocking her down. The group then kicked and stomped on her back and ribs, and ran away.

The victim was taken to Mercy Hospital with bruised ribs. She also said some of her personal belongings were missing, police said.

The other four suspects in the attack have not been arrested.

The attack was just one of more than half a dozen along the Red Line in the past week.

The CTA said it’s working with police to address crime on public transit.