Is a stop and escort of defendants to a police substation justified by reasonable and articulable suspicion of criminal activity?

We need not address whether the initial stop of the defendants was justified by a reasonable and articulable suspicion of criminal activity, see United States v. Woods, 720 F.2d 1022, 1026 (9th Cir.1983), because we find that the stop developed into a de facto arrest when the officers escorted the defendants to the police substation. The Government concedes that it had no probable cause to support an arrest at that point. An arrest made without probable cause is illegal, and evidence or statements seized as a product of illegal detention must be suppressed. Taylor v. Alabama, 457 U.S. 687, 690 (1982).