NASA released a statement Tuesday on the Titan, saying it remains "hopeful the crew will be found unharmed."

"NASA’s Marshall Space Flight Center had a Space Act Agreement with OceanGate, and consulted on materials and manufacturing processes for the submersible. NASA did not conduct testing and manufacturing via its workforce or facilities," the agency said.

-ABC News' Gina Sunseri

The U.S. Navy said it's sending to the search site experts and equipment "designed to provide reliable deep ocean lifting capacity for the recovery of large, bulky, and heavy undersea objects."

The equipment, which can lift up to 60,000 pounds, and the experts will arrive in Canada Tuesday night, the Navy said.

National Security Council spokesperson John Kirby said earlier Tuesday that the Navy was"on standby" to help with the search for the missing submersible, because the Navy has "some deep-water capabilities that the Coast Guard wouldn’t necessarily have."

President Joe Biden is "watching events closely," Kirby said, adding that Biden and the White House offer their thoughts "to the crew onboard, as well as to the -- what is no doubt -- worried family members back on shore."

Three U.S. Air Force C-17 cargo aircraft will be transporting commercial equipment from Buffalo, New York, to Newfoundland, Canada, to help with the search efforts, according to a U.S. official.

-ABC News' Luis Martinez

Efforts to locate the missing submersible are ongoing, and the "complex" search covers an area larger than the state of Connecticut, Coast Guard Capt. Jamie Frederick said at a news conference Tuesday.

Crews are scouring the ocean 900 miles east of Cape Cod and 400 miles south of St. John's, Canada, he said.

The missing five-person crew on the submersible has about 41 hours of oxygen left, Frederick noted.

"We will do everything in our power to effect a rescue," Frederick said.

"We have a group of our nation's best experts," he said, and once the sub is located, "those experts will be looking at what the next course of action is" to rescue the crew members.

"Our thoughts and prayers are with the crew and their families and their loved ones," Frederick added.

OceanGate co-founder Guillermo Söhnlein is coming to the defense of late CEO Stockton Rush, one of those killed in the implosion of Titan, after criticism from director James Cameron, and others, who said the sub's carbon-fiber hull was dangerous.

"In this kind of community, there are completely different opinions and views about how to do things, how to design submersibles, how to engineer them, build them, how to operate in the dives," Söhnlein told the U.K.'s Times Radio on Friday. "But one thing that’s true of me and the other experts, is none of us were involved in the design, engineering, building, testing or even diving of the subs. So it’s impossible for anyone to really speculate from the outside."

Söhnlein co-founded OceanGate in 2009 with Rush and led several dives in the early days of the company. He left OceanGate in 2013, when Rush took over as CEO, but maintained a friendship and spoke to Rush just weeks before the doomed expedition, he said on Facebook.

Cameron, who not only directed the Oscar-winning film "Titanic" but is a prolific ocean explorer, criticized the use of a carbon-fiber hull in the construction of Titan, saying it was only a matter of time before it cracked under the pressure from repeated dives. Rush, in the past, defended its use, saying it had a better strength-to-buoyancy ratio than titanium.

"I was involved in the early phases of the overall development program during our predecessor subs to Titan, and I know from firsthand experience that we were extremely committed to safety and risk mitigation was a key part of the company culture," Söhnlein told Times Radio Friday.