WASHINGTON (CNN) -- Pirates in ships are searching for the lifeboat containing four pirates and their hostage -- the captain of a freighter they failed to hijack earlier this week -- according to a U.S. military official with knowledge of the situation.

Capt. Richard Phillips of the Maersk Alabama is being held by pirates on a lifeboat off Somalia.

The pirates are using ships they have already hijacked and larger ships from which they are launching skiffs, the official said Friday.

One of the pirated ships is the German cargo ship Hansa Stavanger, seized April 4 off the coast of Somalia.

The U.S. military has been monitoring communications between the pirates, the official said. The guided missile frigate USS Halyburton, with helicopter capabilities, has now joined the guided missile destroyer USS Bainbridge in the area. A third ship, the amphibious assault ship USS Boxer, which has a large medical facility on board, will be there within a day.

Richard Phillips, the hostage, tried to escape from the pirates Thursday night by jumping out of the lifeboat, a U.S. official said Friday.  Watch what it's like inside a lifeboat »

Phillips was believed to be trying to swim to the USS Bainbridge, which is in communication with the four gunmen holding Phillips in the 28-foot boat off Somalia's coast, the official said.

Some of the kidnappers jumped into the water, recaptured Phillips, and returned him to the lifeboat, according to the official.  Watch what happened when captain tried to escape »

The pirates fired shots, the military official said, but had no further details.

A Defense Department official told CNN that Phillips appeared to be tied up by the pirates after the escape attempt.

The U.S. official -- who did not want to be named because of the sensitive nature of the situation -- said the escape attempt is being viewed by negotiators as an "optimistic sign" that Phillips is in good health. He has been held since Wednesday, when the hijackers seized control of his U.S.-flagged ship, the Maersk Alabama.  Watch expert talk about hostage escape attempts »

The captain's wife Andrea Phillips thanked everyone for their support in a statement.

"My husband is a strong man and we will remain strong for him," she said. "We ask that you do the same. "

Phillips' 20-man crew regained control of the vessel, and they and the vessel are en route to Mombasa, Kenya, according to the father of one of the crew members.

The ship's owners -- the Norfolk, Virginia-based Maersk company -- would not say how the crew regained control. "There will be time for due diligence and retrospective review once we have the safe return of all parties and the opportunity for a full debriefing," it said in a statement.

For the U.S. Navy, the show of strength is more than just a means to resolve a hostage situation, said Chris Lawrence, CNN's Pentagon correspondent.

Attacks in the area have picked up so drastically in recent months that the Navy has to reposition some of its fleet to deal with the threats, he said. iReport.com: How should the U.S. respond?

The pirates have shown no signs of giving in.

The Maersk Alabama was on its way to Mombasa, Kenya, with a cargo of food aid when it was attacked Wednesday. It was the first time in recent history that pirates had targeted an American ship.

The ship was hijacked some 350 miles off Somalia's coast, a distance that used to be considered safe for ships navigating in the pirate-infested waters.

CNN's Mike Mount and Barbara Starr contributed to this report.
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