<p><strong>Pictured Wednesday, homes lie in ruins after a <a href="http://environment.nationalgeographic.com/environment/natural-disasters/tornado-profile/">tornado</a> blew through Pratt City, a neighborhood in <a href="http://maps.nationalgeographic.com/maps/map-machine#s=r&amp;c=33.54011485511124, -86.86888000000003&amp;z=10">Birmingham, Alabama (see map)</a>, earlier in the day.</strong></p><p>The tornado was one of many spawned by a vast, violent storm system that has so far killed as many as 231 people in six U.S. states as of Thursday, according to CNN.</p><p>At least 131 people have died in <a href="http://travel.nationalgeographic.com/travel/united-states/alabama-guide/">Alabama</a> alone, where several strong tornadoes tore through cities, Governor Robert Bentley told reporters Thursday. <br>"This could be one of the most devastating tornado outbreaks in the nation's history by the time it's over," CNN meteorologist Sean Morris said.</p><p>(<a href="http://environment.nationalgeographic.com/environment/natural-disasters/tornado-safety-tips/">Get tornado safety tips.</a>)</p><p><strong><em>ON TV: </em><a href="http://channel.nationalgeographic.com/channel/series/witness/7051/Overview#tab-Overview">Witness: Tornado Swarm 2011<em> airs Sunday, May 29, 9 p.m. ET/PT &gt;&gt;</em></a></strong></p>