Argentina’s Defence Ministry on Saturday said the missing Argentine Navy submarine with 44 crew members on board had tried to communicate via satellite, Reuters reported. The ministry said they had detected seven failed “satellite calls” they believe came from the ARA San Juan submarine, raising hopes that the crew was alive.

An international search mission has been on in the Atlantic Ocean since the submarine went missing off the coast of Patagonia on Wednesday, The Guardian reported. The signals, which lasted between four and 36 seconds, were detected late on Saturday morning.

The United States Navy has deployed a deep-sea rescue mission to Argentina from California to support the effort. But visibility and movement of rescue vessels has been difficult because of a powerful storm and waves more than six metres high, said Argentine Navy Spokesperson Enrique Balbi.

“The idea is to continue through the night and the early morning, depending on weather conditions,” Balbi said, adding that the weather was likely to improve on Sunday.