Toronto/IBNS: A Royal Canadian Air Force (RCAF) plane has reportedly detected underwater noises while searching for a missing submersible headed for the Titanic, the first potential lead in search since the search started.

The US Coast Guard tweeted that just after midnight EDT on Wednesday both underwater and air searches were "relocated in an attempt to explore the origin of the noises."

But it's not clear whether the sounds are linked to the missing submersible.

The submersible is carrying five passengers that lost contact with its surface ship the Polar Prince early Sunday morning after leaving St. John's, N.L.

The passengers were Hamish Harding, a billionaire and explorer, Paul-Henry (PH) Nargeolet, a French explorer, Shahzada Dawood and his son Suleman, members of Pakistani family, and OceanGate CEO and Titan pilot Stockton Rush.

The tours are owned and operated by OceanGate, a US-based company.

The crews of the US and Canadian coast guards and RCAF have been looking for the vessel that lost contact an hour and 45 minutes into the expedition.

"This is a complex search effort which requires multiple agencies with subject matter expertise and specialized equipment," Capt. Jamie Frederick of the U.S. Coast Guard told reporters during a press conference in Boston on Tuesday.

(Reporting by Asha Bajaj)