The engineer of the No. 110 Metra North Central line train, bound for Chicago, spotted the body on another track just after 7:30 a.m. and contacted police, Metra spokeswoman Meg Reile said.
Lake County Sheriff's officers responded about 8 a.m. and found the body on the tracks south of Deerfield Parkway near the Metra station at 825 Commerce Ct., according to the sheriff's office.
The victim had been struck by an unknown train and was pronounced dead at the scene, the sheriff's office said.
The outbound No. 101, headed to Antioch, was stopped south of Buffalo Grove for about 45 minutes, Reile said. All inbound and outbound trains began moving again about 9 a.m., Reile said.
The woman has been identified as Linda Kozer, 49, of Buffalo Grove. Buffalo Grove police are investigating.
The Sun-Times Media Wire contributed to this report.