WASHINGTON – Police in Montgomery County, Md., received an urgent message about 6:25 p.m. Saturday saying someone had been shot at Wolf Blitzer’s home in Bethesda. Officers streamed toward the CNN host’s residence near the Congressional Country Club. They set up a perimeter.

But a dispatch supervisor was immediately skeptical, and a call to CNN confirmed it: The message was a fraud. Blitzer was fine — was, in fact, out of town. The authorities were dealing with another case of “SWATing,” in which someone jolts police into action with a fake distress call and technological trickery.

Earlier this month, the place was Beverly Hills and the target was “American Idol” host Ryan Seacrest. The caller told police that armed men were trying to break into Seacrest’s place; officers arrived to find nothing amiss. In March, it was Brian Krebs, an Internet security writer and former Washington Post reporter. The caller said Russians had broken in and killed Krebs’s wife. Fairfax County, Va., police, weapons drawn, handcuffed Krebs before they learned that the report was a sham.

Police and emergency communications specialists say the costs of such hoaxes can be tremendous. Scrambling teams of officers can waste tens of thousands of dollars worth of police time, and there are dangers inherent in speeding toward a would-be crime scene or confronting an unsuspecting, albeit innocent, suspect.