All Black legend in drug scandal
This comes after a French report that he tested positive to steroids along with Joe Rokocoko.
Paris-based sports daily L'Equipe reported that the New Zealand internationals failed a drug test after their club Racing 92 beat Toulon in the French Top 14 Final in Barcelona in June.
Their Argentinian teammate Juan Imhoff was also caught in the operation carried out by French Anti-Doping Agency (AFLD), according to the paper.
Carter, widely regarded as the best flyhalf ever, is the game's highest paid star after moving to France following a glittering career with the All Blacks.
The 34-year-old earned 112 caps and won two World Cups with the New Zealanders, racking up a record 1,598 Test points.
He is idolised in New Zealand on a level comparable with David Beckham in Britain or Michael Jordan in the United States.
Any drug taint would be a major blow for New Zealand, which is already reeling from a series of scandals.
But the player's management company, Essentially Group, which also represents Rokocoko, said they were "relaxed" about the situation because Racing's club doctor had filled in all the required documents.
Simon Porter, an Auckland-based player agent with the group, said this meant they had a therapeutic use exemption (TUE) allowing them to use the corticosteroid medication.
"We were reassured that there was nothing to worry about, that there was no wrongdoing, that there was no case to answer for," he told TVNZ.
"It's just a therapeutic use, cortisone is a common drug used to treat pain and inflammation."
Porter added that the players had been "blindsided" by the news being leaked.
"The boys had been told that they had nothing to worry about. They're not enjoying the attention but they're pretty relaxed about it all because they're confident that everything is in order and everything is fine," he said.
Carter was recovering from a calf injury ahead of the Top 14 final, while Rokocoko – a wing who represented New Zealand in 68 Tests – had a knee problem.
Corticosteroids are generally used to reduce inflammation.
L'Equipe said that once alerted by the AFLD, the French Rugby Federation had 40 days to investigate the trio, who all played major roles in Racing's upset win over Toulon.
If the probe failed to find a medical reason for the corticosteroid use, then they could face disciplinary action.
The federation has not yet commented on the report.
It comes a day after All Black scrumhalf Aaron Smith admitted a recent toilet tryst with a mystery woman at a busy airport in Christchurch was a "huge mistake".
Coach Steve Hansen said the 54-Test veteran breached team standards and sent him home from South Africa where the All Blacks play the Springboks this weekend in Durban.
It continues what has been called "the season from hell" for rugby in New Zealand, where image of the nation's number one sport has been battered by off-field controversy.
The New Zealand Rugby Union faced criticism from women's groups last month over its handling of a stripper's allegations that Chiefs players sexually assaulted her during a team night out.
And last week, the organisation made a clumsy U-turn after initially standing by promising teenager Losi Filipo over a vicious street attack on four people, including two women, in Wellington.
Filipo's contract was eventually terminated after a massive public backlash.
Agence France-Presse
