Officer Dan Donakowski confirmed the 27-year-old Hunter was stabbed, but police didn't have any additional information, including where the incident took place, who was responsible and Hunter's condition. The hospital wasn't disclosed.
Detroit police confirmed to NFL.com that Hunter's girlfriend was taken into custody, but they wouldn't provide the suspect's name because the investigation was ongoing.
WXYZ-TV in Detroit said Hunter was knifed in his left shoulder.
The Broncos released a statement saying the team was looking into the matter and hopes Hunter "makes a quick recovery," but that out of respect for his privacy, it wouldn't comment further.
It's not clear how Hunter's stabbing will affect his playing career.
Team doctors are in contact with the physicians who treated Hunter in Detroit, Broncos spokesman Patrick Smyth said.
Hunter's agent, Robert B. Walker tweeted, "I've spoken to my client Jason Hunter and it's a very minor injury, just a few stitches. He'll be fine. We thank you for your prayers."
The stabbing comes just days after police in Florida said Miami Dolphins wide receiver Brandon Marshall, a former Bronco, was stabbed in the stomach by his wife with a kitchen knife.
Hunter's stabbing is the latest difficulty to face the Broncos, who in recent years have dealt with the drive-by slaying of cornerback Darrent Williams, running back Damien Nash's fatal heart attack and receiver Kenny McKinley's suicide.
Last season, Denver linebacker D.J. Williams was stripped of his captaincy after his second drunken driving arrest and cornerback Perrish Cox was charged in a sexual assault case. Shortly after the season ended, running back Laurence Maroney, whose contract is up, was arrested on guns and drug charges in St. Louis.
Hunter was a pleasant surprise at left outside linebacker last year in the Broncos' 3-4 scheme that is being scuttled this season in favor of the traditional 4-3 defense under new coach John Fox. He had a career-high 61 tackles and three sacks, forced a fumble and recovered two, including one he returned for a 75-yard touchdown against Kansas City on Nov. 14.
The Associated Press contributed to this report.