(CNN) -- The underwater search for Malaysia Airlines Flight 370 is on hold -- and probably will be for at least four days -- because of a malfunctioning part on the submersible Bluefin-21 and a broken transponder on the Bluefin's mother ship, the U.S. Navy's deputy director of ocean engineering said Wednesday.
The Bluefin-21 currently is the only submersible looking for the Boeing 777, which was carrying 239 people when it disappeared on March 8 while traveling from Kuala Lumpur, Malaysia, to Beijing.
The Bluefin-21 and the transponder were damaged this week when the vehicle was being hoisted onto the deck of the Australian vessel Ocean Shield. The vehicle struck the navigation transponder, which extends over the side of the ship, said Michael Dean, the U.S. Navy's deputy director of ocean engineering.
Repairs were made to the submersible. But in subsequent tests, operators said the acoustic communications link on the Bluefin-21 and the navigation transponder on the Ocean Shield malfunctioned.
No spare parts for either device were on the ship, Dean said.
Later, he added that the Navy recommended that the ship return to a port to conduct repairs. According to the vessel tracking site MarineTraffic.com, the Ocean Shield has left the search area and is headed toward the Australian coast.
Dean said he is uncertain whether the ship is returning to port, or simply coming within helicopter range of Australia. The Ocean Shield has a helicopter pad.
"Either way, the ship has to get closer to shore," he said.
Parts necessary for the repairs are being shipped from the United Kingdom to Australia, Dean added.
Under a best-case scenario, it will take four or five days to get parts to the ship. But it could take longer if the Ocean Shield has to return to port, Dean said earlier.
The Bluefin-21 had conducted about 18 missions in the south Indian Ocean before the Ocean Shield returned to port to refuel.
But the submersible has been bedeviled with problems since returning to the search site this week.
Shortly after the submersible was placed in the water, Dean said, operators had trouble communicating with it, and they decided to retrieve it. But while they hoisted the Bluefin in 20-knot winds and 3- to 5-foot seas, the Bluefin struck the side of the Ocean Shield and hit the transponder.
The collision damaged the propeller, the tail section and a rear electronics bay, Dean said.
The Ocean Shield's navigation transponder, meanwhile, had internal damage, evidently as the result of the collision, he said.
"The navigation transponder sits on a pole that is extended over the side of the ship, and it can track the ship acoustically," Dean said. "We don't carry a spare transponder."
"Those are just not parts that you would expect to go bad, so they are not parts that you carry," he said.
Dean said some replacement parts have been found, but officials are searching for parts closer to Australia to expedite the repairs.
"We haven't been in the water for two days," Dean said, referring to the submersible. "We've already lost two days. We have another few days to get parts. So it can add up to seven pretty quick," Dean said.