BOSTON -- The captain of a U.S.-flagged cargo ship that was hijacked by pirates off the coast of Africa on Wednesday is still being held hostage, according to a crewmember. The rest of the 20-member American crew was able to overpower the pirates to regain control of the vessel, the Pentagon said.

U.S. officials said an American warship and a half-dozen others are headed to the scene where pirates captured a cargo ship Wednesday with a U.S. crew off Somalia's coast.

Late Wednesday morning, the military confirmed that the crew had regained control of the 17,000-ton Maersk Alabama by overpowering the pirates, taking one pirate into custody and throwing three overboard.

But a crewmember aboard the Alabama later told CNN that the pirates were still holding the ship's captain, Capt. Richard Phillips, hostage. The crew was negotiating for his release.

"There's four Somali pirates, and they've got our captain," crewmember Ken Quinn told CNN.

The crew had a plan to make an exchange for the captain, but the pirates reneged on the deal, Quinn said.

The destroyer USS Bainbridge is headed to the scene, military officials said.

Phillips, who grew up in Winchester, Mass., and currently lives in Underhill, Vt., is a 1979 graduate of the Massachusetts Maritime Academy. Capt. Shane Murphy, a 2001 graduate of the MMA, is second in command, according to his father, Capt. Joseph Murphy, a professor at the academy.

"It has been a harrowing experience for my family and it is a very convoluted story," the elder Murphy said.

The younger Murphy, 34, is married with two sons, ages 3 years and 8 months. He lives with his family in Seekonk.

On his Facebook page, he said he anticipated a run-in with pirates.

"These waters are infested with pirates that highjack (sic) ships daily," Murphy wrote. "I feel like it's only a matter of time before my number gets called."

The Alabama was carrying emergency relief to Mombasa, Kenya, when it was hijacked, said Peter Beck-Bang, spokesman for the Copenhagen-based container shipping group A.P. Moller-Maersk.

It was the sixth ship seized by pirates in a week.

"This is not 'Pirates of the Caribbean.' These are criminals." - Capt. Joseph Murphy

"This is not 'Pirates of the Caribbean.' These are criminals," the elder Murphy said.

Coincidentally, he teaches a new course at the academy about combating high-seas crime.

"The situation is completely out of control. When you have a week and six major ships are taken by pirates, this is a problem that the world has to address," he said.

He said he initially learned about the hijacking from his other son who is serving with the U.S. Navy in the Middle East, and was able to speak to his son after the hijacking.

"It's a whole different world when it becomes personal," he said.

U.S. Sen. John Kerry, D-Mass., released a statement Wednesday night, saying, "These acts of piracy off of Somalia's coastline may seem surreal but they're all too real, and a thorough policy debate is long overdue."

The chairman of the Senate Foreign Relations Committee said he plans to hold hearings to further examine the growing threat. This year alone, there have been more than 60 pirate attacks -- six this week.