<p>HUNTSVILLE, Alabama (CNN) -- A preliminary investigation into last week's fatal school bus crash indicates that a "faulty steering mechanism" on a passing car caused the accident, a police spokesman said Tuesday.</p>
<p>Wendell Johnson said the problem is believed to have caused the teen driver of the 1990 Toyota Celica to lose control of his car and veer into the bus, which dragged along the concrete barrier on the Interstate 565 ramp before plunging 30 feet off the overpass.</p>