POLK COUNTY, Fla. – The Florida Highway Patrol is investigating a fatal crash between three vehicles in Polk County.According to troopers, the crash happened Friday around 10 a.m.Troopers said a sedan and tractor-trailer were both driving west on SR-400 adjacent to one another.According to an FHP report, the sedan failed to stay inside its lane and drove into the center lane and collided with the tractor-trailer.The crash caused the sedan to be pushed into the center median where it collided with a cable barrier, troopers said.Investigators said the sedan continued over the cable barrier and into the eastbound lanes of SR-400 where it struck two other cars and another tractor-trailer.One of the struck cars overturned onto the shoulder while.