HARRISBURG, Pa. (AP) — Federal investigators are looking into the death last week of a trucker killed when a section of electrical conduit fell through his windshield.

The Pennsylvania Turnpike Commission said Monday the National Transportation Safety Board expects to finish its inspection Wednesday and may issue a preliminary report within about a month.

State police say a New Jersey truck driver was killed Feb. 21 when the section of conduit struck him in the head while he was driving through the turnpike's Lehigh Tunnel near Slatington. A coroner has described the conduit as a large pipe and said it damaged other vehicles.

Officials say the Lehigh Tunnel's southbound side is the only tunnel in the turnpike system that has electrical conduit directly above drivers, rather than in a parallel tunnel.