What is the standard of review for a finding that a magistrate erred in concluding that exigent circumstances existed to justify warrantless entry into a house?

On appeal appellants contend the magistrate erred in concluding that exigent circumstances existed to justify warrantless entry into the Pine Street house. The existence of exigent circumstances is a question of fact, and "the proper standard of review of a finding regarding exigent circumstances is whether the finding was clearly erroneous." United States v. Flickinger, 573 F.2d 1349, 1356-1357, (9th Cir. 1980) (footnote omitted). This court must determine, in reviewing the findings of the district court, whether "on the entire evidence (it) is left with the definite and firm conviction that a mistake has been committed." Id. at 1357.