Southbound traffic on Interstate 75 into Hillsborough County became thwarted Tuesday after a crash involving a pedestrian. 

According to the Florida Highway Patrol, a woman was struck by a tractor trailer along the highway at 3:35 a.m. 

Troopers said the woman was walking in the center lane of southbound I-75 near the I-275 apex for unknown reasons when she was struck by a tractor trailer.   

She sustained life-threatening injuries and was airlifted to Tampa General Hospital, according to officials. Her condition is unknown.

As a result of the crash, the center and inside southbound lanes of I-75 were closed north of Bruce B. Downs Boulevard.

That created a large backup on I-75 and even on I-275 into downtown Tampa. 

The crash remains under investigation.