Four members of the touring England rugby team have refused to answer police questions about an alleged incident at the Hilton Hotel in Auckland early last Sunday.
But in first confirmation of some details of the incident police say they are investigating a "serious sexual assault".
The police say the allegation was "that a woman was raped and/or sexually assaulted by four players."
The city's Adult Sexual Assault Team flew to Christchurch to interview the players.
"The players have advised police - via legal representation this morning - that they are declining to be interviewed by Police on the matter at this stage," police spokeswoman Noreen Hegarty said.
The England team have a touring lawyer with them, Queen's Counsel Richard Smith.
Ms Hegarty said police would continue their investigation.
"Any decision about where to take matters from there will depend on the outcome of that review.
"While no formal statement has been made by the woman who made 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."
Police have said they are investigating a "serious allegation" involving up to four players in a room at the Hilton, on Auckland's waterfront, early last Sunday. No formal complaint has been received.
English newspaper The Sun yesterday quoted team sources saying that a woman was involved in a "threesome" with two players, while two others watched, but she was a willing participant.
Christchurch lawyer Nigel Hampton, QC, said it was unusual for police to investigate and interview witnesses without a formal complaint.
"If nobody has formally complained, I can't see why it's even in the hands of the police," he said.
"It seems to be a wild goose chase. I am mystified."
Hampton said the England team's in-house lawyer would probably be telling the players not to talk to police as there was no formal complaint.
"Everybody has the right not to talk to police and they'd just be saying 'no thanks'," he said.
The Sun quoted a source close to the team saying an 18-year-old woman willingly had sex with two players while another two watched early last Sunday.
"Two players admitted three-in-a-bed sex with the girl," the source said.
"She'd pursued them from the start and phoned the Hilton to find out where they were drinking."
The players claim the woman was calm and in good spirits when she left early on Sunday.
Hours later, team chiefs had a call from police revealing a "serious allegation" had been made. It is understood the initial allegation was made by the woman's boyfriend.
The Daily Telegraph reported that England rugby officials were confident the incident was nothing more than a "storm in a teacup" and that no player would be charged.
"All the players have been allowed to travel from Auckland to Christchurch and that is an indication of what the police think about the situation," a Rugby Football Union official told the newspaper.
England captain Steve Borthwick told a press conference in Christchurch yesterday that morale in the camp was high in the face of the allegations. "We are a very tight group and we are all looking forward to the game this weekend."
The Sun said incoming England boss Martin Johnson was furious at stories of boozed-up stars and phoned tour coach Rob Andrew.
