BUENOS AIRES — The Argentine Navy on Thursday signaled that it had given up hope of finding the 44 crew members aboard a submarine that appeared to have experienced a calamitous event in mid-November. The announcement was almost certainly an acknowledgment of the largest loss of life aboard a submarine in nearly two decades.

Capt. Enrique Balbi, a navy spokesman, said the operation to find the submarine, the San Juan, had been downgraded from a rescue mission to a search for the remains of the vessel.

Some relatives of crew members reacted angrily to the decision and complained that they first learned about it on the news.

“This measure destroyed the last bit of hope I had,” Luis Tagliapietra, the father of one of the missing sailors Alejandro Damián Tagliapietra, told the cable news channel Todo Noticias. “I want to know what happened for real, because I don’t believe the official hypothesis at all. They lie to us.”