The Haixun 01 detected the second signal for 90 seconds late yesterday afternoon, about 2 kilometers (1.2 miles) from where a pulse was noticed the previous night, retired Air Chief Marshal Angus Houston, head of Australia's Joint Agency Coordination Centre, said today. The U.K.'s HMS Echo and Australian defense vessel Ocean Shield are being directed to the area, where the water is about 4.5 kilometers deep, he said.

"The fact that we've had two detections, two acoustic events in that location, provides some promise," Houston said at a press briefing in Perth. "We're running out of time in terms of the battery life on the emergency locator beacon."

The Haixun 01 had detected a pulse with a frequency of 37.5 kilohertz while searching in the southern Indian Ocean, China's official Xinhua News Agency said yesterday. While black-box locator beacons transmit at that frequency, the signal hasn't been confirmed as related to the missing Malaysian Airline System Bhd. jet, the news service reported, citing the China Maritime Search and Rescue Center.