Nigerian military officials were hunting on Friday for two Americans kidnapped at sea off Africa's west coast, an area that has become a fertile ground for pirates in recent years.
"Yes, we are aware that they are missing, but we still do not have any information on the whereabouts of the men," Nigerian navy spokesman Kabiru Aliyu said. "But we have deployed search-and-rescue teams who are currently combing the creeks. We are doing our best to find them."
Aliyu told NBC News that the ship had been found, but did not give more details other than to say it was "somewhere off Bonny in the Eastern Naval Command Area of Responsibility."
U.S. officials confirmed to NBC News that two Americans were taken early on Wednesday in an area plagued by pirates, criminal gangs and active militant groups. The pirates boarded the ship and singled out the Americans -- the captain and chief engineer -- and took them ashore as hostages, U.S. officials said.
"We believe this was an act of piracy," State Department spokeswoman Marie Harf told reporters. "At this point, we do not have information that would indicate this was an act of terrorism. Obviously, our concern at this point is for the safe return of the two U.S. citizens."
U.S. officials were closely monitoring the situation and seeking more information, Harf added.
“This is not a Hollywood movie plot,” former State Department official Andrew Shapiro said on the TODAY show on Friday. “Piracy and hijackings threaten our economic security and put innocent lives at risk.”
Nigerian officials echoed American officials saying they believed that the abductions had been carried out by "criminals" and not politically motivated militants.
Maritime news website gCaptain reported that the captain and chief engineer of oil supply vessel C-Retriever had been abducted. Meanwhile, C-Retriever's insurer Skuld told NBC News that the ship was "not under the control of pirates."
A U.S. defense official said the State Department and FBI were leading the American response to the incident. A second defense official said the U.S. Marine Corps has a small training unit in the region but it was not clear if it would get involved.
State Department spokeswoman Jen Psaki said Friday afternoon that U.S. officials in Nigeria had been in touch with their local counterparts but that no further information was available.
“We continue to seek additional information about the incident,” she told reporters. “We're not going to outline details publicly, in part because our primary concern is the rapid return of these -- of these two citizens. And we're continuing to coordinate with appropriate parties, but I really don't have any additional public update at this point.”
Louisiana-based Edison Chouest Offshore, the ship’s owner, remained silent Friday and had likely been advised not to comment, said Rory Lamrock, a maritime analyst at U.K.-based security firm AKE.
"The companies are probably advised to say nothing to the media," he said. "It is generally because hostage-takers are very clued up and have access to the Internet, have access to the news. [Companies] don't want to say anything that can be used against their workers."
While piracy off Somalia and the Horn of Africa on the east coast of Africa have been falling off in recent years, it has skyrocketed by more than 30 percent this year as ships passing through West Africa's Gulf of Guinea, a major commodities route, and come under threat from gangs wanting to snatch cargoes and crews.
This makes them targets for criminals and raises insurance costs. Kidnapped sailors and oil workers taken in Nigerian waters are usually released after a ransom is paid.
In an interview with NBC News’ Brian Williams on Thursday, American cargo ship Capt. Richard Phillips, who was taken hostage off the coast of Somalia in April, 2009, said the waters off Nigeria were “worse than even Somalia."
U.S. Navy SEAL snipers killed the three Somali pirates and rescued Phillips, who had offered himself as a hostage to save his crew. His high-seas hijacking has been turned into a film starring Tom Hanks. "Captain Phillips" earned more than $52 million during its first two weeks in cinemas.
In the first nine months of 2013 the Gulf of Guinea accounted for all crew kidnappings worldwide, 32 of them off Nigeria, and two off Togo, according to the International Maritime Bureau. In such incidents, sailors are taken ashore and usually held for ransom.
NBC News’ Marian Smith, Matthew DeLuca and Alastair Jamieson contributed to this report. Senan John Murray, an independent journalist based in Nigeria, and Reuters also contributed.