Missing Titanic sub search continues as oxygen runs out

(CNN) – A massive search has been underway to locate the missing Titanic sub.

France is sending a ship to aid U.S. and Canadian emergency crews.

The frantic search to find the missing Titanic expedition sub is expanding. Five more ships are expected to join the rescue efforts Thursday bringing the total to ten.

U.S. Coast Guard Jamie Frederick said, “This is an incredibly complex search operation.”

The search has now expanded to 10,000 square miles as of Tuesday.

Planes are also searching by air. France is now aiding U.S. and Canadian crews.

Captain Frederick said, “We are incredibly grateful for the full spectrum of international assistance.”

But as oxygen levels dwindle so does hope. Officials worry there are just hours of breathable air left on board.

Former Royal Navy Commander Ryan Ramsey said, “Five people in a small submersible, all breathing out carbon dioxide with no ability to remove that carbon dioxide for this length of time becomes the problem.”

There was a glimmer of hope Wednesday as sonar buoys detected sound in the water. But it’s unclear if the noises are actually coming from the sub.

One expert says the five people on board the OceanGate sub, including the company’s CEO, would know that making sound is their only chance of being found.

RMS Titanic Inc. Senior Adviser for Strategic Initiatives David Gallo “You want to let people know you’re alive. And he knows unless he makes that kind of a sound, that’s the only chance they have in the pitch black of the deep sea.”