Sounds detected by probes deep in the Atlantic did not come from an Argentinian submarine lost for six days, the country’s navy said, dashing hope among relatives of the 44 sailors aboard.

Navy spokesman Enrique Balbi said the “noise” was analysed and experts determined it was probably “biological”. He said the sounds did not come from tools being banged against the hull of a submarine as was previously reported.

“We all had hope, but unfortunately this comes from believing sources that are not trustworthy,” Mr Balbi said. “Some sources were saying that this was banging on the hull in Morse code signals.”

The noise was heard by two navy ships about 220 miles from the Argentinian coast and at a depth of about 650ft. A US Navy P-8 Poseidon aircraft was sent to help in the effort to isolate the source of the sounds.

The San Juan went missing last week as it sailed from the extreme southern port of Ushuaia to Mar del Plata. More than a dozen international vessels and aircraft have joined the search, which has been hindered by stormy weather that has caused waves up to 20ft. The first reports off trouble came when the submarine reported a battery failure and was returning to base. It then went missing.

Brief satellite calls over the weekend had originally been thought to indicate the crew was trying to re-establish contact, prompting emotional celebrations by family members and officials. But Mr Balbi said later that officials analysed the seven low-frequency satellite signals and determined they were not received from the submarine.

Although the German-built diesel-electric vessel carried enough food, oxygen and fuel for the crew to survive about 90 days on the sea’s surface, the sub had only have enough oxygen to last seven days submerged, Mr Balbi said.

At the Vatican, Pope Francis, a native of Argentina, said he was sending “fervent prayers” for the crew.

The US Navy ordered its Undersea Rescue Command based in San Diego, California, to deploy to Argentina to support the search for the submarine.

Pledges of help also came from Chile, Uruguay, Peru, Brazil and Britain, which was sending a polar exploration vessel, HMS Protector.