NASHVILLE, Tenn. --

Two people were killed when an ambulance was involved in a crash with a Tennessee Department of Transportation truck on Interstate 65 North on Thursday afternoon.

The crash occurred near the Wedgewood Avenue exit 80 at about 2:50 p.m. The driver of the ambulance, who was an off-duty Franklin, Tenn., firefighter, and a patient inside the ambulance were killed in the wreck.

"The ambulance was traveling without the emergency lights and transporting an elderly woman from her dialysis treatment back to her retirement home. For reasons unknown at this time, the ambulance rear-ended the TDOT truck," said Kristin Mumford, Metro Police.

An off-duty Metro firefighter, who was inside the ambulance and working as an EMT for the ambulance company, was also hurt in the wreck. He was taken to Vanderbilt Medical Center and in critical condition.

The driver of the TDOT vehicle, Robert Green, was in stable condition at Vanderbilt Medical Center.

The ambulance belongs to a private company that was based in Franklin, Tenn.

When the crash occurred, the TDOT truck was pulled over in the emergency lane without its hazard lights on.

However, TDOT policy says the lights only have to be flashing when a worker is outside the vehicle helping a driver. So, it was still unclear why the TDOT truck had pulled over.

Copyright 2009 by WSMV.com. All rights reserved.This material may not be published, broadcast, rewritten or redistributed.Got a story idea? E-mail newstips to news@wsmv.com or call the newsroom 24/7