(CNN) -- Somali pirates hijacked a yacht with four Americans onboard in the Indian Ocean, U.S. military officials said Saturday.

The identities of the Americans were not immediately known, but the yacht, the S/V Quest, is owned by Jean and Scott Adam, according to Ecoterra International.

It is not clear whether the Adams -- who were on a worldwide cruise -- are onboard.

The U.S. military is prepared to intervene in the situation if necessary, said Rear Adm. Charles Gaouette, deputy commander of the U.S. Navy's Fifth Fleet, based in Bahrain.

"They were part of a sailing group that set sail from the southern tip of India into the western Indian Ocean," he said, adding that the situation is being monitored with U.S. Central Command.

Gaouette said there is no reason to believe the hijacked yacht has been taken to the coastline of Somalia yet, though pirates in the region have been known to do so.

Another U.S. official, who asked not to be named due to the sensitivity of the situation, said the United States is determining what military assets are in the region and the capabilities of the personnel onboard. The official said that the pirates are believed to be onboard the yacht with the Americans, and the next step would be to determine whether the military could keep the yacht from reaching the shore -- either by blocking or harassing it.

Authorities said the yacht was en route from India to Oman when it was captured Friday. The Adams' website documents their worldwide voyage, which started in late 2004. It includes trips to New Zealand, China, Cambodia and Panama.

"If the owners are onboard, it would be a sad log for the couple on their seven-year world journey," Ecoterra said.

The Adams were traveling with a group of somewhere between 14 and 30 other yachts taking part in what's called the Blue Water Rally, said Scott Stolnitz, a boater who described himself as a longtime friend of the couple.

Stolnitz said Scott Adam had told him several weeks ago that he was concerned about pirate activity in the area, which he had never visited before, but was determined to traverse the world himself as opposed to shipping the boat -- as some other yacht owners have done.

"They weighed their options and decided they would join the rally for safety," Stolnitz said.

On their website, the Adams say their mission "is to allow the power of the Word to transform lives ... (and) seek fertile ground for the word and homes for our Bibles."

A post earlier this year said they would refuel in Djibouti waters, another pirate flash point.

"Djibouti is a big refueling stop," said the post, which is not dated. "I have no idea what will happen in these ports, but perhaps we'll do some local touring."

Piracy has flourished off the coast of Somalia, which has not had an effective government for two decades. In April 2009, pirates seized the U.S.-flagged Maersk Alabama, leading to a standoff in the Indian Ocean.

U.S. forces moved to rescue American Capt. Richard Phillips after seeing a pirate aiming a weapon on his back, officials said at the time. Three pirates were killed and one was arrested.

The Somali man arrested was sentenced to more than 30 years in prison.

CNN Pentagon Correspondent Barbara Starr contributed to this report.