NEWPORT, Ind. -- A false alarm from a system that alerts residents in three western Indiana counties to problems at the Newport Chemical Depot sent schools scrambling to start taping their doors and windows to keep out potentially harmful fumes, officials said.

Word that it was a false alarm circulated throughout Fountain, Parke and Vermillion counties about 15 minutes after it sounded Wednesday, but not before school action plans had already been set into motion, school officials said.

"I immediately alerted my staff to shelter in place," Ronda Foster, principal at Ernie Pyle Elementary School in Vermillion County, told the Tribune-Star of Terre Haute. "We were in the process of taping when we got the word that it was a false alarm."

A couple children did cry when they saw their teachers rushing to start taping the doors and windows to make the rooms airtight, Foster said.

The depot stores about 1,200 tons of deadly VX nerve agent that the government plans to soon start destroying.

Vicki Francis, spokeswoman for the Chemical Stockpile Emergency Preparedness Program in Vermillion County, said the alarm was activated by accident during routine testing of the system. Mike Costello, principal at Van Duyn Elementary School in Clinton, said he heard the alert and immediately called emergency management to find out what was going on.

In minutes, he said he was on the school radio telling the other Vermillion County schools that it was a false alarm.

Leonard Orr, superintendent of the Southwest Parke Community Schools, said the alarm "is something we don't take lightly. We're at a point here, when that baby goes off, we jump."

Orr added that when it does sound, "it takes about 10 seconds to get your heart beating again."