ISTANBUL, Nov. 30 — A Turkish passenger jet crashed in the mountains of western Turkey early Friday, killing all 57 people on board, including several prominent nuclear physicists on their way to a conference, Turkish authorities said.

The plane, a McDonnell Douglas MD-83 operated by Atlasjet, an airline based in Istanbul, took off from Istanbul and disappeared from radar shortly before it was due to land at the airport in Isparta. It crashed about seven miles from the airport, near the town of Keciborlu, the authorities said. The cause of the crash was unclear. The weather was good, airline officials said.

The plane crashed in an area that was not on its scheduled route, according to Semsettin Uzun, the governor of Isparta Province. “We don’t understand how it landed there,” he said.

The Associated Press quoted Ali Ariduru, in charge of Turkey’s civil aviation authority, as saying that there were no signs that either terrorism or sabotage had caused the crash.