BOSTON — An advanced submersible vessel belonging to an Everett-based company and its five-person crew went missing Sunday evening while exploring the Titanic shipwreck in the North Atlantic Ocean.

Everett-based OceanGate Expeditions owns the deep-sea craft and charges for trips down 2½ miles to the Titanic. The submersible, called the Titan, can hold five people.

The Titan crew launched from the Canadian research ship Polar Prince into the ocean Sunday morning 900 miles off Cape Cod, according to the U.S. Coast Guard First District in Boston. The ship’s crew lost contact with the vessel about 1 hour and 45 minutes into the dive.

The submersible was reported overdue around 9:13 p.m. Sunday about 435 miles south of St. John’s, Newfoundland, the Joint Rescue Coordination Centre in Halifax, Nova Scotia told the Associated Press.

The vessel has an emergency sustainability capacity of 96 hours, U.S. Coast Guard Rear Adm. John Mauger said during a press briefing Monday afternoon.

On Monday morning the U.S. Coast Guard launched a search-and-rescue mission with assistance from the Canadian Coast Guard. Search efforts included a C-130 Hercules airplane and a Canadian P8 aircraft with underwater sonar technology.

“It is a remote area, and it is a challenge to conduct a search in that remote area,” Mauger said. “We need to make sure that we are looking both on the surface, for the vessel if it had surfaced back to the water but had somehow lost communications to the vessel, but we also have to search the water column.”

Nobody answered the unmarked door Monday at the OceanGate headquarters in the back of the Port of Everett’s Craftsman District Boat Repair Yard.

The four windows in the bay door were covered. One window had a sticker that said “OceanGate Titanic Survey Expedition 2019.”

OceanGate’s focus was on those aboard the vessel and their families, according to a statement posted to Twitter.

pic.twitter.com/JmH8e47zuI— OceanGate Expeditions (@OceanGateExped) June 19, 2023

“We are deeply thankful for the extensive assistance we have received from several government agencies and deep sea companies in our efforts to reestablish contact with the submersible,” the company’s statement said. “We are working toward the safe return of the crewmembers.”

Lt. Cmdr. Len Hickey said a Canadian Coast Guard vessel and military aircraft were assisting the search effort, the Associated Press reported.

The electric sub has been used to take tourists and scientists deep into the ocean at various sites for commercial and research missions. The vessel’s Titanic trip features a padded stadium seat, sandwiches, bottled water and a restroom the size of a milk crate, according to a 2021 story in The Daily Herald.

The initial group of tourists was funding the expedition by spending anywhere from $100,000 to $150,000 apiece.

The Titan completed its first expedition down about 13,000 feet below the ocean’s surface to the Titanic wreckage in 2021.

The 10-day Titanic expedition included eight days aboard a six-story, 300-foot support vessel with a crew of 50, the Herald story reported.

On June 14, OceanGate Expeditions tweeted:

“The wreck of the Titanic lies about 400 miles off the coast of Newfoundland. Without any cell towers in the middle of the ocean, we are relying on @Starlink to provide the communications we require throughout this year’s 2023 Titanic Expedition.”

Photos show people in the support vessel in the water apparently heading to the site of the Titanic wreckage. The Titan is not shown.

In a May 2021 court filing, OceanGate said the Titan had an “unparalleled safety feature” that assesses the integrity of the hull throughout every dive, the AP reported.

At the time of the filing, Titan had undergone more than 50 test dives, including to the equivalent depth of the Titanic, in deep waters off the Bahamas and in a pressure chamber, the company said.

During its expedition in 2022, OceanGate reported that the submersible had a battery issue on its first dive, and had to be manually attached to its lifting platform, according to a November court filing.

“In the high sea state, the submersible sustained modest damage to its external components and OceanGate decided to cancel the second mission for repairs and operational enhancements,” the filing stated.

More missions, however, followed. The company reported that 28 people visited the wreck site last year, according to the AP.

The wreck of the Titanic lies about 400 miles off the coast of Newfoundland. Without any cell towers in the middle of the ocean, we are relying on @Starlink to provide the communications we require throughout this year’s 2023 Titanic Expedition.

More: https://t.co/F7OtKI0En7 pic.twitter.com/wr7HeKlGjj— OceanGate Expeditions (@OceanGateExped) June 14, 2023

The submersible weighs 23,000 pounds and holds four crew and a pilot. Its hull is made of 5-inch thick carbon fiber that can withstand up to 160 million pounds of pressure, The Herald reported. Its controls were based on a Logitech video game controller, Kenneth Hauge, one of the company’s submersible pilots, told The Herald in 2021.

The Titan putters along at 2 to 3 mph, with views out Titan’s 7-inch thick acrylic window, Hauge said in 2021. It takes about 10 hours to reach the Titanic and return.

Titan’s controls are based on a Logitech video game controller. OceanGate worked with NASA to build the fully-electric submarine. Lithium batteries, which charge overnight, power the sub, Hauge said.

The sub was on display at the Port of Everett in December 2021.

A Herald story in July 2022 told of a an upcoming mission later that summer.

OceanGate was developing a new sub with a target depth of 18,000 feet.

Check back for more on this developing story. The Associated Press contributed to this report.

Andrea Brown: 425-339-3443; abrown@heraldnet.com; Twitter: @reporterbrown.

Ben Watanabe: 425-339-3037; bwatanabe@heraldnet.com; Twitter: @benwatanabe.