"United States medical professionals will conduct a formal analysis of presumed human remains that have been carefully recovered," the agency said.
On board were British explorer Hamish Harding, French submarine expert Paul-Henri Nargeolet, Pakistani-British tycoon Shahzada Dawood and his son Suleman, and Stockton Rush, CEO of the sub's operator OceanGate Expeditions.
They presumably died instantly when the Titan sub, about the size of an SUV car, imploded under the crushing pressure of the North Atlantic at a depth of more than two miles.
Mangled debris recovered from the small submersible was offloaded earlier in the day in eastern Canada, bringing to an end a difficult search-and-recovery operation.
That debris will now be taken aboard a US Coast Guard cutter to a US port for further analysis, the organisation said.
"There is still a substantial amount of work to be done to understand the factors that led to the catastrophic loss of the Titan and help ensure a similar tragedy does not occur again," said the leader of the US probe into the tragedy, Captain Jason Neubauer.
Television images showed what appeared to be the Titan sub's nose cone and a side panel with electronics and wires hanging out being hoisted from a ship onto a flatbed truck at a Canadian Coast Guard terminal in St. John's, Newfoundland.
Pelagic Research, the New York company that owns the Odysseus remote-operated vehicle used in the search for the ill-fated submersible, said its offshore search-and-recovery operation has wrapped up.
Titan was reported missing on June 18 and the US Coast Guard said last Thursday that all five people aboard the submersible had died after the vessel suffered a catastrophic implosion.
A debris field was found on the seafloor, 1,600 feet (500 meters) from the bow of the Titanic, which sits more than two miles (nearly four kilometers) below the ocean's surface and 400 miles off the coast of Newfoundland.
The announcement of the implosion ended a multinational search-and-rescue operation that captured the world's attention since the tourist craft went missing.
The Coast Guard has launched its highest level of probe, called a Marine Board of Investigation, into this accident.
