A shooting took place Tuesday near Harrison's North Philadelphia bar, a source told Anthony Gargano of Philadelphia's WIP Radio.
Harrison's agent, Tom Condon, told ESPN's Chris Mortensen on Friday: "I've spoken with Marvin and I've spoken with his attorney, and they say the reports are erroneous. Marvin was not involved in any shooting, and he is not the subject of this investigation."
Condon declined to answer any other questions.
Harrison was interviewed by police about the shooting, Philadelphia Police Lt. Frank Vanore said. Harrison has not been arrested or charged.
"He was interviewed," Vanore said Friday. "Why he was interviewed, that is all part of the investigation. No one is a suspect."
A source told the Philadelphia Daily News that Harrison, during an interview with police, later admitted to being in a fistfight on Tuesday, but the Colts receiver said he wasn't involved in the shooting.
According to ESPN's Sal Paolantonio, the case will be taken over by Philadelphia District Attorney Lynne Abraham. Paolantonio also reports that the case is now on the back burner as police searched for bank robbery suspects who killed a police officer in North Philadelphia this weekend.
After the first day of Colts rookie minicamp on Friday, Indianapolis coach Tony Dungy said he knew little more than had been reported.
"My phone has been ringing, too, but I don't have any details," Dungy said. "I really don't have any more information than you do."
NFL spokesman Greg Aiello said Friday the league was "aware of the report, and we are looking into it."
According to WIP's report, the source said the alleged victim came into the bar, Playmakers, about 5 p.m. and engaged in an argument with Harrison. The victim then left the bar, heading to his car, with Harrison following. Gunfire broke out and the victim was hit in the hand.
A source told the Philadelphia Daily News that a 2-year-old boy suffered a cut under his eye from glass that shattered when an errant bullet hit a car windshield, according to police. Originally it was reported that a young girl had been injured.
Police came to the scene, but the victim did not identify a shooter.
On Wednesday, according to the WIP report, a source said ballistic tests showed that the gun that had fired the shots was a custom-made Belgian weapon, and police determined that Harrison owned such a gun. A source told ESPN.com's John Clayton that the gun is registered.
Police then went to a Philadelphia car wash owned by Harrison to question him about the gun. Harrison admitted owning such a weapon but claimed it never left his suburban Philadelphia home.
However, WIP's source said the gun was discovered in a bucket at the car wash, and tests showed that it had fired bullets that matched those found at the scene.
The source said police were contacted Friday by an attorney representing a second alleged victim in the shooting, and police are now waiting for that individual to come forward.
Harrison, a prep football star at Philadelphia's Roman Catholic High, has owned Playmakers since July 2004, according to state records.
Harrison has played his entire 12-season career with the Colts and is the franchise's record holder in every major receiving category: receptions (1,042), yards (13,944), touchdowns (123) and 100-yard games (59). The 35-year-old is one of only four players in league history to top 1,000 receptions.
But after eight consecutive Pro Bowl appearances, last season was the most frustrating of Harrison's career.
He injured his left knee against Denver on Sept. 30, missed all but five games and finished with 20 receptions for 247 yards and one TD.
Team president Bill Polian said in February that Harrison was recovering from offseason arthroscopic surgery on his right knee and had been rehabilitating the inflamed capsule in his left knee. He was not expected to be completely healthy for the start of Indianapolis training camp July 24.
The typically quiet Harrison has a reputation for being humble on and off the field.
But he's still one of the Colts' most visible players -- and their longest-tenured veteran. Harrison, along with Peyton Manning and Edgerrin James, were nicknamed Indy's triplets in the late 1990s. He was a first-round draft pick in 1996 out of Syracuse and wound up as the best receiver in a class that included Keyshawn Johnson and Eric Moulds.
Off the field, Harrison was sued after the 2005 Pro Bowl when three boys accused him of attacking them when they tried to get his autograph. The suit alleged Harrison "violently and physically attacked" the minors, including placing a "potentially deadly choke hold" on one of the boys, but it was later dismissed.