CHICAGO -- Chicago police are investigating a woman's claim that she was kidnapped, sexually assaulted and held captive for days.The woman was walking to a bus stop in the Englewood neighborhood near the 6700 block of South Halsted Street last Saturday when she said a man in a pickup truck pulled over and punched her in the side of the head. He dragged her into his truck and drove her to a home in an unknown location and locked her in the basement, Chicago police said.She was sexually assaulted by multiple people over a 6-day period, police said. She was let go Friday.Police said the man was in his early 40s with a bald head, black beard and brown eyes. He was between 6 feet and 6 feet, 2 inches tall with a medium build.He was driving a older model, navy blue four-door pickup with rust over the wheels, police said.Anyone with information is asked to call Area South detectives at 312-747-8271.