Advance warnings of a coming EF-5 tornado were no help to those injured or killed in Joplin, Missouri. They might even have discouraged action, according to an assessment issued by the National Oceanic and Atmospheric Administration Tuesday.

The majority of Joplin residents surveyed did not immediately go to shelter upon hearing the initial warning, whether from local warning sirens, television, NWR [National Weather Radio,] or other sources,” the report states. “Instead, most chose to further clarify and assess their risk by waiting for, actively seeking, and filtering additional information.”

These delays were probably the result of a widespread skepticism about alert sirens, which were perceived as going off frequently and for low consequence events, such as heavy rain or thunderstorms.

“All sirens mean is there is a little more water in the gutter,” said one person surveyed in the report.

However, some of those who died might have taken precautions, National Weather Service Meteorologist and assessment team leader Richard Wagenmaker told the Associated Press.

“It's really hard to tell how many people that perished in the tornado did not take shelter,” he said. “It was a very large tornado, so there were certainly a number of people who did all the right things, took shelter in the best available place, but still found themselves in situations that weren't survivable. So it's really hard to make that assessment.”

The report includes several recommendations, including continued education for businesses, improved warning systems that provide clear, consistent messages and avoid “user complacency,” and better collaboration with local partners to provide better warning.