CHICAGO (CBS) — Blue Line service to and from the West Side was delayed Monday after a woman died on a train.

The Chicago Transit Authority said the Blue Line was experiencing delays beginning about 3:30 p.m. because of a sick customer at the UIC-Halsted stop in the median of the Eisenhower Expressway.

Trains in both directions ran on one track between the Jackson and Racine stops. Normal service was restored after a few hours.

But police said the 49-year-old woman died on the train after suffering a medical emergency.

The Cook County Medical Examiner’s office will determine the exact cause of the woman’s death.