The National Weather Service said its radar wasn't able to detect Muscatine's tornado when it moved through the city Monday.
The storm was moving so fast that by the time a severe thunderstorm warning was issued, the tornado was already forming.
Muscatine County Emergency Management said the city waits for a tornado warning before initiating the outdoor warning sirens. Since it never got that warning - the sirens never went off.
Emergency Management said it has gotten hundreds of complaints about the warning failure.