Tomorrow, police will drill through a concrete slab at a Detroit home where Jimmy Hoffa may be buried. They are responding to what they say is a "credible" tip from a man who claims he saw a burial take place at the home in 1975 around when Hoffa vanished. "We don't believe it's Jimmy Hoffa," said Police Chief Jim Berlin, quoted in the Macomb Daily. "I am very skeptical," Dan Moldea, author of "The Hoffa Wars" who also heard from the same tipster, told CNN. Once police have a core sample, it'll be tested for human remains. If the sample tests positive, they'll start digging.