WASHINGTON: The Pentagon identified four US victims in Saturday's crash of a surveillance aircraft in southern Afghanistan and said the incident appeared unrelated to Taliban violence.

The police chief in Zabul province, Rogh Lewanai, told Reuters on Saturday that bad weather caused the plane to crash, in the district of Shahjoi. At the time, Nato did not identify the nationality of the victims but said they were part of Nato's International Security Assistance Force (Isaf).

The Pentagon said on Sunday the crash of the MC-12 was under investigation.

Zabul, wedged between Kandahar and Ghazni, has seen much violence in recent weeks, including a suicide bomb attack in early April that killed a young U.S. diplomat, several US soldiers and an unnamed US civilian.

Dozens of Afghan civilians also have been killed there this month.

The Pentagon said all four victims were airmen: Captain Brandon Cyr, 28, of Woodbridge, Virginia; Captain Reid Nishizuka, 30, of Kailua, Hawaii; Staff Sergeant Daniel Fannin, 30, of Morehead, Kentucky; and Staff Sergeant Richard Dickson, 24, of Rancho Cordova, California.