A 36-year-old man was beaten to death by a group of teenagers in attack in Center City subway concourse this afternoon, police said.

One person was taken into custody and police said they were still looking for at least three others who fled the scene.

The incident happened at 13th and Market Streets in the concourse of a busy Septa stop about 2:45 p.m., said Officer Jillian Russell of the Public Affairs Unit.

Septa spokeswoman Sylvana Hoyos said a Septa police sergeant initially responded and administered CPR to the victim until medics arrived. Septa police will investigate the incident while the Philadelphia Police Department will investigate beating and the death, authorities said.

Police said the Septa sergeant was on the eastbound side of the concourse when he saw what appeared to be a confrontation between numerous teens and the man who appeared as if he trying to fend off the attack on the westbound side. When the transit officer immediately went to assist the man, the teenagers fled, authorities said.

The victim was taken to Thomas Jefferson University Hospital where he was pronounced dead at 3:09 p.m., police said.

A homicide detective said authorities were sorting through information surrounding the beating and expected to have more details available later.

Contact staff writer Barbara Boyer at 215-854-2641 or bboyer@phillynews.com