Travis Decker Search, Bones Discovered Near Daughters' Dump Site

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.

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 only his DNA -- was found on the plastic bags covering his late daughters' heads. Their deaths were pronounced a homicide, as the county medical examiner ruled they died by suffocation.

Authorities have been looking for Decker ever since ... though, given this new update from the feds ... it's possible Decker has been dead a while.

The search for Decker has been extensive, to say the least. His pickup was found not long after the Decker girls were discovered dead ... 150 miles outside of Seattle and in a heavily forested area.

Some wondered if Decker had fled into the wilderness, citing his military background as a possible way he may be able to escape capture.

There's currently a warrant out for his arrest ... he's been charged with 3 counts of first-degree murder.