A 44-year-old man died Thursday morning while trying to cross I-75 South in Marietta, police said.

The man, who has not been identified, was crossing near the entrance ramp to South Marietta Parkway around 2:30 a.m. when he was struck and killed by a tractor-trailer, according to Marietta police. The truck driver stayed at the scene and is cooperating with the investigation.

It was not clear why the man was walking on the interstate. His name is being withheld pending family notification.

All southbound lanes were blocked for at least two hours while police investigated, finally reopening just after 5 a.m., according to the WSB 24-hour Traffic Center.

Anyone with information is asked to contact investigators at 770-794-5384.

— Please return to The Atlanta Journal-Constitution for updates.