3:24 PM PT -- A spokesperson for the Nashville Police Dept. tells TMZ Sports ... initial indications are Madsen suffered "a medical emergency" while driving on I-65 North.
The spokesperson said officers received calls about a motorist blocking a lane on the interstate and when they arrived on scene, they found Madsen unconscious in the driver's seat of the car.
Police say they broke into the vehicle via the passenger side window and removed Madsen and immediately started chest compressions.
Sadly, after transporting Madsen to a nearby hospital, he died.
A cause of death is still unknown at this time.
Sad news in the NFL ... replay official Carl Madsen died on Sunday shortly after working the Kansas City Chiefs vs. Tennessee Titans game in Tennessee.
He was 71 years old.
The NFL announced the tragic passing on Monday -- with league reporter Tom Pelissero saying Madsen died "while en route home" from the Week 7 matchup at Nissan Stadium in Nashville.
No other information surrounding his death has been given.
Madsen -- a veteran of the U.S. Air Force -- was an on-field official for the NFL from 1997 to 2008 ... before he became a replay official for the league in '09.
"Carl Madsen was an NFL officiating fixture for more than two decades, first as a highly respected on-field official before transitioning to a replay role beginning in 2009," NFL senior VP of officiating training and development Walt Anderson said.
"A terrific friend and colleague, Carl's love of football and dedication to officiating was ever-present, as he generously shared his time to mentor young officials at clinics across the country. A veteran of the Air Force, Carl had a tremendous spirit and will be greatly missed."
#RIP
Originally Published -- 2:47 PM PT