Rescue crews searching for a submersible in the north Atlantic are focusing on underwater noises detected by Canadian aircraft, but warned they had not yet determined whether those sounds originated from the missing vessel.

“We can’t tell you what the noises were and — we think this is the most important point — we are searching where the noises are,” said Jamie Frederick of the US coast guard, which is coordinating the search, at a press conference on Wednesday afternoon. 

The vessel is estimated to have enough oxygen to sustain the five passengers on board until Thursday morning. The search area has been expanded to an area of about 10,000 square miles and 2.5 miles deep, with five surface vessels scouring the area and another five en route to the scene.