ST. LOUIS (AP) -- A woman trying to get away from a man who was beating her crawled onto an interstate highway and was struck and killed by a tractor-trailer, police said Friday.

The tractor-trailer driver left the scene. Police were looking for both the truck driver and the man who allegedly beat the woman.

Police don't yet know the victim's name. She was not wearing identification, police spokeswoman Schron Jackson said.

It happened just before 5 a.m. on Interstate 44 near the Grand Boulevard exit in St. Louis. Witnesses told police they saw the man and woman fighting on the shoulder of the interstate.

Witnesses reported the man knocked the woman to the ground, then began kicking her in the head. She crawled on the pavement to get away and moved from the shoulder to a driving lane, where she was stuck by a tractor-trailer. She died instantly, Jackson said.