PERTH, Australia — Authorities are confident signals detected deep in the Indian Ocean are from the missing Malaysian jet’s black boxes, Australia’s prime minister said today, raising hopes they are near solving one of aviation’s most perplexing mysteries.

Tony Abbott told reporters in Shanghai that crews hunting for Flight 370 have zeroed in on a more targeted area in their search for the source of the sounds, first heard on Saturday.

“We have very much narrowed down the search area and we are very confident that the signals that we are detecting are from the black box on MH370,” Abbott said.

“Nevertheless, we’re getting into the stage where the signal from what we are very confident is the black box is starting to fade,” he added.

The plane’s black boxes may hold the answers to why the Boeing 777 lost communications and veered so far off course when it vanished March 8.