The smoke incident happened during the cruise phase of a scheduled flight between Raleigh-Durham, NC and Atlanta. Delta Flight DAL 1819, with more than 250 passengers and crew on board, was diverted to GSP. The aircraft landed safely and taxied unassisted to a gate, where passengers deplaned. Passengers were later transferred to Atlanta by bus.
A preliminary report about the March 19, 2008 incident has been posted to the FAA website. It says:
While in flight, a heating duct imploded, spraying insulation throughout the cabin. Aircraft diverted to Greenville/Spartanburg Airport, Greer, SC.A news story and accompanying video clip about Flight DAL 1819 on WYFF4 in Greenville quoted passengers who said that the smoke appeared to come up through the floor in the back of the cabin. Passengers described seeing smoke and "ashes," and feeling heat. They reported hearing "the sound of grinding metal from the cargo area."
Flight attendants reportedly moved passengers away from the smoky area to the front of the plane, and prepared the cabin for the emergency landing. Although the FAA preliminary report did not mention a fire, several news reports said that fire extinguishers were deployed in the cabin before the plane landed.
[Photo Source]