Canadian police have obtained a video "consistent" with media accounts that it shows Toronto Mayor Rob Ford smoking crack cocaine, but they would not confirm the contents of the video.
Ford, who has denied he smokes crack, said he could not comment on the matter because the video is evidence in a separate case before the courts. But he said he would not quit his job.
"I wish I could come out and defend myself. Unfortunately I can't because it's before the courts, and that's all I can say right now... I have no reason to resign," he told a throng of reporters outside his office.
In the first official link between Mr Ford and a high-profile Toronto drugs investigation, Toronto Police Chief Bill Blair identified the mayor as a subject in a video recovered during the probe.
"I can tell you that the digital video file that we have recovered depicts images which are consistent with those that had previously been reported in the press," Mr Blair said.
"I think it's fair to say the mayor does appear in that video, but I'm not going to get into the detail of what activities are depicted on the video."
Mr Ford made international headlines in May, after US mediablog Gawker and the Toronto Star newspaper said their reporters had been shown a video that appeared to show him smoking crack.
Gawker raised funds to buy the video but said it was unable to re-establish contact with the seller. Blair's comments offered the first confirmation that the video exists.
Mr Ford said in May he could not comment on "a video that I have never seen or does not exist."
Mr Ford, previously a cost-cutting councillor on a divided Toronto city council, was elected mayor in 2010, and he insists he will run again when his term expires next year.
Mr Blair said police had not interviewed Ford and the contents of the video itself did not support charges against the mayor.
"There is nothing on that video that would allow us to form reasonable grounds that would support the laying of a criminal charge," he said.
But he admitted to some concern.
"This is an issue of significant public concern and I think that is a problem for the city," he said.
Mr Blair was speaking following the release of court documents detailing police evidence gathered in drug charges earlier this month against Mr Ford's friend and part-time driver Sandro Lisi.
The documents detailed hundreds of contacts between the two men in the weeks between the first reports of the video and Mr Lisi's arrest on drug charges on 1 October.
Police said they had added a charge of "extortive efforts to retrieve a recording" against Mr Lisi, whose lawyer refused to comment, according to the Star.
The partially redacted 474-page file, released to Canadian media and published on their web sites, showed the reports on the alleged crack video in May had triggered the police drugs investigation, dubbed Project Brazen 2.
Mr Ford gleans most of his support from the suburban regions at the edge of Toronto. But a poll released this week showed his approval rating has fallen to 39% from 49% in the last month.