More debris and suspected human remains have been recovered from a privately owned submersible that failed catastrophically in June while on a mission to the Titanic, the US Coast Guard said.

All five people on board the recreational sub, named Titan and operated by US-based company OceanGate, were killed when the vessel imploded, which is believed to have occurred during its June 18 descent.

The sub's failure was confirmed on June 22, ending a days-long rescue mission that captivated the world.

The Coast Guard has launched its highest level of probe, called a Marine Board of Investigation, into the accident.

"Marine safety engineers with the Coast Guard's Marine Board of Investigation (MBI) recovered and transferred remaining Titan submersible debris and evidence from the North Atlantic Ocean seafloor" on October 4, the US Coast Guard said in a statement Tuesday.

"Additional presumed human remains were carefully recovered from within Titan's debris and transported for analysis by US medical professionals," it added.

Some wreckage and presumed human remains were also recovered in late June.

The Coast Guard said it was coordinating with the US National Transportation Safety Board "and other international investigative agencies to schedule a joint evidence review of recovered Titan debris."

The five men aboard the Titan 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.

A debris field was found 1,600 feet (500 meters) from the bow of the Titanic, which sits 400 miles off the coast of Newfoundland.

The victims were presumed to have died instantly when the Titan, about the size of an SUV car, imploded under the crushing pressure of the North Atlantic at a depth of more than two miles (nearly four kilometers).

The US Coast Guard and Canadian authorities have launched probes into the cause of the tragedy, which occurred after the Titan lost contact about an hour and 45 minutes after plunging into the ocean.

The Titanic hit an iceberg and sank in 1912 during its maiden voyage from England to New York with 2,224 passengers and crew on board. More than 1,500 people died.

It was found in 1985 and has become a lure for nautical experts and underwater tourists.