Sulaiman said military was suspecting that bad weather caused the crash.
Military helicopter crash kills 13
He said the helicopter was carrying personnel to reinforce a police operation against Islamist militants operating in the district of Poso.
He said Poso was the scene of deadly Muslim-Christian violence in 1999-2000, and the area has since become a known hotbed of militant activity.
Spokesman said last week police killed two suspected Islamist fighters from China's Uighur ethnic group in a gunfight in Poso as part of an operation to crush a group led by a wanted militant named Santoso.
Sulaiman said more than 2,500 military and police personnel have been deployed in the area since January.
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