In what circumstances will the court uphold a search warrant for contraband found in plain sight during a search for additional suspects?

In Block we concluded that the search there in question was 'a lawful search' for additional suspects. In that case an officer, after arresting the defendant and five others downstairs in a house during an apparent 'pot party,' went upstairs looking for possible suspects and there observed contraband in plain sight. In sustaining the search we stated (at p. 245, 98 Cal.Rptr. at p. 661, 491 P.2d at p. 13) that the officer 'had reasonable cause to believe, based upon facts available to him at the time he acted, that additional persons might be on the premises.' We noted that specified matters known to the officer indicated [7 Cal.3d 316] that a 'pot party' was in progress involving an undetermined number of participants and that the lights illuminating the stairway and upstairs hall justified the further suspicion that other persons might be upstairs who were involved in the offense or who might pose a security risk for the arresting officers. We concluded that under the circumstances it was reasonable for the officer to act as he did and that contraband found in plain sight during the course of that search for suspects was properly seized. (See also United States v. Briddle, 436 F.2d, 4, 7--8 (cert. den. 401 U.S. 921, 91 S.Ct. 910, 27 L.Ed.2d 24), wherein court upheld seizure of evidence observed in plain sight during the agent's 'conceded right to conduct a quick and cursory viewing of the apartment area for the presence of other persons who might present a security risk.')