Vallejo Police are investigating a fatal solo car crash, the department said Wednesday. Around 5 p.m. Tuesday, police received a report of a collision at Sonoma Boulevard and Chestnut Street in south Vallejo, where officers and medical personnel found a woman inside a crashed car. The woman was transported to a hospital where she later died, according to the department. "Investigators believe the driver may have experienced a medical emergency before the collision," said the department. Substances do not appear to have played a role in the crash, but an autopsy is required before the woman's cause of death can be determined, police said.