(KMOV) -- It was the first time that St. Louis County's 138 new sirens were used since being installed, but a number of KMOV Facebook fans reported that the sirens went off after the storm had passed.
"Sirens went off about ten minues after the worst part of the storm passed," Hillary Walters, of Ferguson, posted.
"Came on after all the wind, pouring rain and hail had already passed," Tina Asher, of Affton, added.
Duffy Barney, a St. Louis County official, said the storm may have passed many area houses by the time any rotation was spotted on the radar and the warning was issued.
The county's policy when sounding the sirens is to play it safe and sound them countywide.
Duffy said that all of the sirens operated properly, but eleven more will be added to in certain areas to fill in some gaps in the system.