San Francisco police said on Friday they had helped Apple Inc security search for a lost item, following a week of reports that a prototype of the newest iPhone had gone missing in July.

Officers did not say exactly what Apple had lost, but they left a clue -- the San Francisco Police Department's Friday press release about the hunt was called iphone5.doc, an apparent reference to a new version of the mobile phone that tech industry watchers expect to be released soon.

Apple declined to comment on the matter.

Tech news service CNET this week said an iPhone 5, which has not been released, went missing in a San Francisco bar in July. SF Weekly, a local newspaper, on Friday quoted a San Francisco man as saying police had come to his house in July searching for a lost iPhone.

Although a prototype of the iPhone 4 went missing in 2010, police said this time Apple had tracked the lost item to a San Francisco house and four police accompanied two Apple employees to the house.

The two Apple (security) employees met with the resident and then went into the house to look for the lost item. The Apple employees did not find the lost item and left the house, the police statement said.

It did not say why police accompanied Apple security or the circumstances under which Apple employees went into the house to look for the lost item. Police did not respond to a request for further comment.

SF Weekly quoted a 22-year-old man who described himself as the resident of the searched house as saying the group identified themselves as police and that none had said they were working for Apple. They had traced the phone to the house using satellite positioning software on the device but did not find anything in the house, he said he was told.

The man, identified by SF Weekly as Sergio Calderon, could not be reached for comment by Reuters.

Police, meanwhile, gave different versions of events during the day on Friday, while Apple has declined to comment at all.

Hours before San Francisco police issued their statement about the search, SFPD spokesman Lieutenant Troy Dangerfield denied that police had been contacted by Apple in connection with any lost phone, or by the person visited by Apple security and the police.

No one has reported anything, Dangerfield told Reuters.

In general, Dangerfield said SFPD requires a supervisor's approval for personnel who are not law enforcement officers to accompany police during investigations.

It's not routinely done at all, Dangerfield said.

(Reporting by Peter Henderson and Dan Levine)