"Ocean Shield has been able to reacquire the signals on two more occasions, late yesterday afternoon and later last night," said Angus Houston, head of the Joint Agency Coordination Centre.
"Ocean Shield has now detected four transmissions," he said as searchers try to poinpoint wreckage from the Malaysian Airlines Boeing 777 that disappeared on March 8 with 239 people on board.
The last two transmissions were picked up on Tuesday. The first lasted five minutes and 32 seconds and the second approximately seven minutes.
He told a press conference that experts analysing the first two pulse signals detected by an Australian ship earlier this week believe they are consistent with a flight data recorder.
"They believe the signals to be consistent with the specification and description of a flight data recorder," Houston said.
The retired air marshal said he was confident the hunt was now in the right area but a sighting of wreckage was needed to be certain.