The US Coastguard confirms remote underwater vehicles were redeployed in response to reports of banging to explore the origin of the noises.
It said the searches have yielded negative results but continue.
The 21ft Titan vessel lost contact with research vessel Polar Prince around one hour and 45 minutes into the vessel’s dive towards the Titanic wreck on Sunday morning.
Five people are on board the Titan, including a British billionaire Hamish Harding and the chief executive of OceanGate Inc, Stockton Rush, Titan’s operator as well as Paul-Henri Nargeolet, a former commander in the French navy and Pakistani businessman Shahzada Dawood and his son Suleman.
The US Coast Guard says the vessel has the capacity to stay underwater for 96 hours – and in the recent briefing officials believe it has around 40 hours of oxygen remaining.
