Police in Los Angeles are beginning an investigation into an incident in which filmmaker Mel Gibson is alleged to have made anti-Semitic comments.
The 50-year-old star has fought alcoholism in the past
Mr Gibson, 50, was alleged to have made the comments after being arrested for drink-driving in Malibu, California.
He later apologised for his outburst, admitting saying things "that I do not believe to be true and which are despicable", but did not give details.
His apology was "unremorseful and insufficient", campaigners have said.
On the Anti-Defamation League's website, national director Abraham Foxman said the statement released by Mr Gibson did not constitute "a proper apology".
The New South Wales Board of Jewish Deputies, in Australia, said about Mr Gibson's alleged outburst that "one can only shake one's head in dismay and think where does that come from".
Mr Gibson was stopped by police at about 0235 local time (0935 GMT) on Friday after allegedly driving at 87mph in a 45mph zone.
The star was booked for drink-driving and freed on bail.
However, entertainment website tmz.com links to what it says is a copy of a suppressed police report which notes a series of anti-Semitic comments from the actor during the arrest.
In a statement on Saturday, Mr Gibson said: "I acted like a person completely out of control when I was arrested, and said things that I do not believe to be true and which are despicable.
"I am deeply ashamed of everything I said and I apologize to anyone who I have offended."
He added: "I have battled the disease of alcoholism for all of my adult life and profoundly regret my horrific relapse."
The Los Angeles County Sheriff's Department is to begin investigating the incident.
The Office of Independent Review, a Sheriff's Department watchdog panel, is investigating whether officers covered up the alleged outburst, chief attorney Mike Gennaco told the Associated Press news agency.
Sheriff Lee Baca denied that his department were trying to cover up Mr Gibson's alleged behaviour.
"There is no cover-up. Our job is not to (focus) on what he said. It's to establish his blood-alcohol level when he was driving and proceed with the case," Sheriff Baca told the Los Angeles Times.
Steve Whitmore, a spokesman for the department, also would not comment on what Mr Gibson said but he added that the department would eventually release details of the arrest, the New York Times reported.
"Nothing will be sanitised," Mr Whitmore said in a statement.
Mr Gibson won a best director Oscar for his 1995 film Braveheart, in which he also starred.
His 2004 biblical epic, The Passion of the Christ, was recently named the most controversial movie to date by US magazine Entertainment Weekly.
A devout Catholic, Mr Gibson shot the film depicting the last 12 hours in the life of Jesus Christ in Aramaic and Latin. It took more than $600m (£337.5m) worldwide
His new film Apocalypto is set 3,000 years ago in central America and features dialogue spoken in an obscure Mayan dialect.
Mr Gibson is also known for several other works, including the Lethal Weapon and Mad Max series of films in which he starred.
Mel Gibson statement in full:
"After drinking alcohol on Thursday night, I did a number of things that were very wrong and for which I am ashamed.
"I drove a car when I should not have, and was stopped by the LA County sheriffs.
"The arresting officer was just doing his job and I feel fortunate that I was apprehended before I caused injury to any other person.
"I acted like a person completely out of control when I was arrested, and said things that I do not believe to be true and which are despicable.
"I am deeply ashamed of everything I said and I apologize to anyone who I have offended.
"Also, I take this opportunity to apologize to the deputies involved for my belligerent behaviour. They have always been there for me in my community and indeed probably saved me from myself.
"I disgraced myself and my family with my behaviour and for that I am truly sorry.
"I have battled the disease of alcoholism for all of my adult life and profoundly regret my horrific relapse.
"I apologize for any behaviour unbecoming of me in my inebriated state and have already taken necessary steps to ensure my return to health."