EXCLUSIVE

XXXTentacion‘s murder case has expanded beyond the scope of the Broward County Sheriff’s Dept. in Florida … TMZ has learned federal investigators are also involved in tracking down his killers.

Sources familiar with the situation tell TMZ … the U.S. Marshals and Broward County Sheriff’s Dept. are on an intense hunt to track down at least 2 other suspects who disappeared after Dedrick D. Williams was arrested last week for murder.

We’re told the Marshall has been at the forefront from the beginning … the Office played a major role with the Broward County Sheriff’s Dept. in nabbing Dedrick. But as we first reported … cops believe 3 people were involved in the murder of the 20-year-old rapper, and arrest warrants have been issued for the remaining 2.

TMZ broke the story … XXX was gunned down in his car outside a motorcycle shop in Pompano Beach. It’s unclear if the killers knew XXX or if it was a robbery.