WINTER PARK, Fla. - A motorized wheelchair exploded early Thursday inside a Winter Park home, sparking a fire, officials said.  The fire broke out around 2 a.m. on McKean Circle off Palmer Avenue. 
 According to authorities, the battery on the wheelchair may have caused the explosion. 
 A couple and two dogs inside the home were not injured. 
 Smoke caused extensive damage to the home, firefighters said. 
 The state fire marshal is investigating.