U.S. space agency officials looking into what caused the space shuttle Columbia to disintegrate as it re-rentered the earth's atmosphere, say initial indications show an unexplained, dramatic rise in temperature.

Just minutes before Columbia broke into pieces in the sky, something caused the spacecraft's left side, just above the wing, to suddenly heat up and tilt to the left.

"The temperature rose 60 degrees over five minutes," he said.

Shuttle Program Manager Ron Dittemore says investigators are looking into what happened in the following minutes.

"We had an increase in drag on the left side of the vehicle. Does this mean something to us? We're not sure. It can be indicative of rough tile, it can be indicative of missing tile. We're not sure yet," he said.

A small piece of debris had hit heat-resistant tiles on Columbia's left wing during blast off, something NASA examined at the time, but decided was insignificant. But it has now become an early focus of the investigation.

However, space agency officials caution that, at this point, information is very preliminary and could change from day to day. In the meantime, recovery crews continue to search for shuttle debris and human remains.