Signals from two locations in the ocean around the Philippines appeared to be from the H2A rocket that Japan launched in late November carrying two spy satellites to monitor North Korea, said Junichi Moriuma, a spokesman for the Japan Aerospace Exploration Agency (JAXA).

"We have picked up signals that appear to be from the rocket but we cannot be sure," he said. The signals came from an area where the rocket's debris was expected to splash down, he added.

The ship's sonar equipment broke down shortly after discovering the signals on January 1, causing the ship to head back to Japan Wednesday for repairs before resuming the search.

The signals are 5,000 to 6,000 meters (16,200 feet to 19,500 feet) deep, making a recovery mission "difficult", Moriuma said. But if successful, it could lead to clues into the accident.

JAXA blew up the rocket and its cargo after its booster rocket failed to separate from the main rocket, making the craft too heavy to reach its planned orbit.

Analysts say the failure has delayed the implementation of Japan's satellite defense program and hampered its commercial launch vehicle ambitions.

SPACE.WIRE