The pilot of a Circuit City (search) jet did not indicate any trouble and its approach to the Pueblo (search) airport appeared normal just before the plane crashed, killing eight, investigators said.

"The descent profile of the plane looked OK," National Transportation Safety Board chief investigator Frank Hilldrup (search) said late Thursday. The last radar reading indicated the plane was about 300 feet above ground, but he said it was too early to say if the jet engines were operating normally.

NTSB chairwoman Ellen Engleman Conners (search) said the investigation will include the weather and potential mechanical problems. Freezing drizzle and fog were reported at the time of the crash Wednesday morning.

Aviation officials had warned about icing conditions and the pilot of another plane reported light to moderate icing, Hilldrup said. The pilot of that plane activated an in-flight deicing system.

The twin-jet Cessna Citation C-560 (search), owned by electronics retailer Circuit City, was stopping to refuel when it crashed. Four employees, two outside business partners and two pilots were killed, the company said.

Neither Circuit City nor the Pueblo County coroner has released their names.

Investigators recovered the plane's cockpit voice recorder and were interviewing witnesses and getting records on the aircraft and its crew. Investigators also removed the voice recorder from the second plane, which is also owned by Circuit City.