The alleged incident took place in Auckland's Hilton Hotel
Four England rugby players are being investigated after an allegation of sexual assault, possibly of rape, New Zealand police have confirmed.
The four players allegedly involved have declined to be interviewed by police over the claim at this stage.
No formal statement has been made by the woman who made what police called a "serious sexual assault allegation".
The alleged incident was said to have occurred in a private room at the Hilton Hotel, Auckland, on Sunday.
It is claimed it took place early on Sunday, after England's defeat in the first Test against New Zealand.
Members of the Adult Sexual Assault Team flew to Christchurch where the squad is now based, hoping to talk to the four players, who have not been identified.
Rob Andrew could not be drawn on the police inquiry
But a police spokeswoman said the players had advised police, via legal representation, "that they are declining to be interviewed by police on the matter at this stage".
She went on: "Auckland City Police will continue to investigate the allegation - that a woman was raped and/or sexually assaulted by four players - as thoroughly as possible before reviewing the file.
"Any decision about where to take matters from there will depend on the outcome of that review."
The spokeswoman said no formal statement had been made by the woman behind the allegations.
"A formal complaint can be made at any time in the future and police are then obliged to assess the evidential basis of that complaint," the spokeswoman added.
The BBC's Nick Bryant, in Christchurch, said that under New Zealand law the players were not obliged to speak.
Rugby Football Union (RFU) chief executive Francis Baron told BBC News the players were acting on legal advice by not speaking to the police.
"No complaint has still been made, the police therefore are unable to progress their investigation," he said.
"We are desperate to clear the players' names but we're in a very strange situation - with no allegations, no complaint being made - as to exactly how the name of the players can be cleared."
In a statement, the RFU said the four players "continue to deny the allegations" and had received legal advice.
It read: "In the absence of any formal complaint in this matter the players were advised to decline the request made to them to voluntarily attend upon the police and it is fully within their rights to do so.
"The players continue to deny the allegations and have the full support of the England management, coaches and players."
The England team play the All Blacks in Christchurch on Saturday.
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