SYDNEY, Australia — An Australian search vessel has detected two more sets of signals that might originate from “black box” flight recorders from the Malaysia Airlines jetliner missing for more than a month, an Australian official coordinating the search for the plane said on Wednesday.

The official, Angus Houston, said the new clues would help narrow the hunt for wreckage from the aircraft.

“What we’re picking up is a great lead,” Mr. Houston told a news conference in Perth. “I’m now optimistic that we will find the aircraft, or what is left of the aircraft, in the not too distant future.”