WASHINGTON — The familiar, piercing tone of an emergency alert jolted television viewers to attention. Then came the frightening images: the White House surrounded by terrorists, landmarks in flames in the nation’s capital and military convoys patrolling the city. “THIS IS NOT A TEST,” read the on-screen advisory.

It was, however, a hoax.

The warning, intended to summon viewers not to shelters but to movie screens, was a commercial for “Olympus Has Fallen,” an action thriller released in March 2013 to middling reviews but decent box-office results. And the Federal Communications Commission was not amused.

On Monday, the commission leveled fines totaling $1.9 million on three of the nation’s biggest media companies — Comcast, Viacom and Disney — for “willfully and repeatedly” violating federal law by carrying the commercial.

It was a mere 30 seconds, not a sustained hourlong deception of the sort Orson Welles pulled off in radio’s golden era in “War of the Worlds.” Still, even the fleeting fictional use of the signal — meant to alert Americans to an urgent message from the president or an impending natural disaster — was enough to set off alarm, the commission said.