Florida Highway Patrol officials say that around 3:35 a.m., an adult female was walking in the center lane of southbound I-75 near mile-marker 272 for unknown reasons when she was struck by a tractor trailer.
The pedestrian sustained serious, life-threatening injuries and was airlifted to Tampa General Hospital for medical care.
FHP Troopers remain on scene investigating the incident.
TRAFFIC: Significant volume and reduced speeds, I-275 S/bound approaching Busch Blvd. Motorists, please maintain safe following distances. pic.twitter.com/YpFRX4C7Vg