The National Football Post first reported the story this morning, saying the altercation occurred Aug. 5, according to a police report. Napa Police Lt. Brian McGovern told the Web site that he isn't permitted to reveal the identity of the injured person.
"It's an internal matter, and will be handled as such," Raiders senior executive John Herrera said.
Cable has not mentioned the incident in any of his news conferences. Two team officials confirmed that Hanson was not at practice Sunday.
The website said that Napa police responded to Queen of the Valley Hospital on Aug. 6 in response to Hanson seeking treatment for his injured jaw.
"(The hospital) is required to report those things to the police department any time someone comes in the victim of an assault-type crime," McGovern told the website. "We were dispatched to the hospital and ended up contacting the victim at that location. The victim said the assault had occurred the previous day at the Raiders' training camp facility.
"Basically, he said he had been assaulted by a member of the staff but refused to identify who that person was. There isn't anything we can do if the victim is uncooperative in providing us with any additional information as far as witnesses or suspect information."
Hanson was suspended by former coach Lane Kiffin for one game last season after Hanson criticized Kiffin for not having the Raiders well prepared for the regular-season opener against the Denver Broncos.
Hanson could not be reached for comment.