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.

The United States Coast Guard commander leading the search for a missing submersible off the coast of Newfoundland, Canada, said Tuesday morning that crews in multiple aircraft have flown over an area of the Atlantic Ocean "roughly about the size of Connecticut" while "looking for any signs of surfacing."

"As we continue on with the search, we're expanding our capabilities to be able to search under the water as well," Rear Adm. John Mauger, commander of the First Coast Guard District, told ABC News' Robin Roberts during an interview on "Good Morning America."

A commercial vessel with remotely operated vehicles is now on scene that will allow rescuers to search underwater, according to Mauger.

"This is a complex case," he added. "The Coast Guard doesn't have all the resources to be able to affect this kind of rescue, although this is an area that's within our search zone."

In many cases, Mauger said, the Coast Guard's role is to coordinate all of the assets and technical expertise that can be used in a search, in addition to operating aircraft or ships when necessary.

"In this particular case, we've established a unified command with the United States Navy, with the Canadian Armed Forces, with the Canadian Coast Guard and with the private operator OceanGate Expeditions to make sure that we understand what's needed and deploy all available equipment to the scene that could be used to locate this submersible, whether it's on the surface or down beneath the surface," he said.

Crews have been working "around the clock" to locate the deep-sea vessel since it lost contact with its operator on Sunday morning, according to Mauger.

In the last 24 hours, a Canadian aircraft has been dropping sonar buoys into the water that can pick up sound the submersible may be emitting. Vessels that have the capability to listen with their own sonar equipment are also on scene, according to Mauger.

"If they are making sound, that's certainly one of the ways that we're going to use to locate them," he said.