A rugby fan told told the rugby365.fr website he witnessed a drunk Kelleher being injured in a street brawl after a car chase.
The incident happened after Kelleher allegedly crashed into another vehicle, the Sunday News reported.
He faces up to two months on the sidelines in France's Top 14 competition, after injuring his shoulder following the alleged scuffle with the damaged car's owners.
Toulouse-based newspaper La Depeche du Midi also reported the halfback required hospital treatment for a fractured bone in his face.
French police said Kelleher, 32, had been drinking before the incident.
The fan said a scuffle broke out after the car owners confronted Kelleher and his friends. Punches and kicks were traded before Kelleher was knocked down.
"Kelleher remained on the ground a while," the fan said.
Kelleher was arrested and held in custody overnight.
Toulouse prosecutor Michel Valet said police were investigating whether to lay charges.
"When the police intervened, they saw that the motorist that had caused the crash was a famous rugby player," Mr Valet said. "And it was clear that he had been drinking."
Toulouse manager Guy Noves said the club would have to make further inquiries before deciding on any action against Kelleher.
Kelleher joined Toulouse after the All Blacks' failed 2007 Rugby World Cup campaign.
He became an overnight hit with the high-flying club's fervent fans, after helping inspire the team to the Top 14 title last year.
