FBI / Chelan County Sheriff's Office Composite

The ongoing manhunt for suspected killer Travis Decker may have a major update ... bones were found near where his daughters' bodies were discovered, TMZ has confirmed.

For those who haven't been following the case ... Decker's daughters -- Paityn, 9; Evelyn, 8; and Olivia, 5 -- were found dead on June 2 at campground near Leavenworth, WA -- with the father's whereabouts unknown. A massive manhunt was launched shortly thereafter. FBI

An FBI spokesperson tells TMZ ... "We can confirm that some bones were collected as part of the search activity earlier in the week around the Rock Island Campground. These bones will be further analyzed to determine if they are animal or human."

Decker became the main suspect after his DNA -- and onl

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