The U.S. Coast Guard announced via Twitter early Thursday that a remotely operated vehicle (ROV) deployed by the Canadian vessel Horizon Arctic has reached the sea floor, beginning its search for the missing submersible.

Meanwhile, the French vessel L'Atalante is preparing its ROV to enter the water in the search area, the U.S. Coast Guard said.

Time is running out as rescuers race to locate and save five people trapped in a submersible that vanished during a tour of the Titanic wreckage on Sunday morning.

The deep-sea vessel submerged at 8 a.m. ET on Sunday with a 96-hour oxygen supply, according to the U.S. Coast Guard. That amount of breathable air is forecast to run out on Thursday morning.

The search and rescue mission remains ongoing.

The New York Times traced the lineage of Wendy Rush, wife of missing OceanGate CEO Stockton Rush, and found that she's the great-great-granddaughter of a couple who died on the Titanic, Isidor and Ida Straus.

The executive director of the Straus Historical Society told ABC News that The Times article, which cites archival records, is largely correct with regard to Wendy Weil Rush's heritage.

-ABC News' Nic Uff

A U.S. Navy portable crane system capable of bringing up items from as deep as 20,000 feet has arrived in St. John's, Newfoundland, but is waiting to be welded onto a chartered ship to take it to the search area for the missing submersible, according to a U.S. Navy official.

The Navy has not yet contracted a ship for the salvage system, known as Fly Away Deep Ocean Salvage System or FADOSS, the official told reporters Wednesday. Once the ship is contracted, Navy teams will spend approximately 24 hours working around the clock to weld the system aboard the ship before it can leave port, the official said.

FADOSS is the salvage system the U.S. Navy uses for all of its deep-water recoveries. Last year, it was able to bring up an F/A-18 aircraft that had fallen into the waters of the Mediterranean Sea.

-ABC News' Luis Martinez

A submersible on a tour of the Titanic wreckage was reported overdue by its operator OceanGate Expeditions on Sunday, prompting the United States Coast Guard to launch a search and rescue effort for the 22-foot, 23,000-pound vessel.

Designed with life support to sustain five crew members for 96 hours, the submersible would need to be rescued in three days to save its five passengers, according to the Coast Guard.

Stockton Rush founded Washington-based OceanGate in 2009 to make deep-sea exploration more accessible to scientists and tourists. Fourteen years, more than 200 dives and three submersible designs later, the company now finds itself in a desperate search to recover the submersible carrying five people aboard that’s gone missing off the coast of Newfoundland, Canada.

OceanGate confirmed Monday it had lost contact with a submersible, saying in a statement: "We are exploring and mobilizing all options to bring the crew back safely. Our entire focus is on the crewmembers in the submersible and their families. We are working toward the safe return of the crewmembers."

Here's what we know about the submersible.

-ABC News' Peter Charalambous and Sam Sweeney