File: A Maersk cargo ship like the one pirates attempted to hijack for a second time off Somalia.
File: The USS Bainbridge, a guided missile destroyer sent to the scene where pirates captured a vessel with a U.S. crew off Somalia's coast.
File: Capt. Richard Phillips of Underhill, Vt., captain of the U.S.-flagged cargo ship Maersk Alabama.
File: Capt. Shane Murphy, second in command aboard the Maersk Alabama.
FBI agents planned to interview the crew of a U.S. cargo ship Saturday as the bureau began building a criminal case against Somali pirates who attacked the ship and took the captain hostage.
The Maersk Alabama arrived safely in Kenya on Saturday, three days after Somali pirates stormed the ship, failed to hijack it, and fled in a lifeboat with the captain.
"The FBI has informed us that this ship is a crime scene," John Reinhart, president of Maersk Shipping Line said Saturday, explaining why crew members cannot immediately leave the ship.
"It has moved from the rescue to investigation," he said. "After the investigation, we then move to repatriation, which is bringing our heroes home.
"Now with the Alabama safely in port, this is an FBI program. They're in control."
Whether criminal charges ever get filed could depend on how the standoff between Navy warships and the pirates ends. The pirates are adrift in the Indian Ocean with Capt. Richard Phillips serving as hostage — and likely the only thing keeping them alive.
The pirates, who are far outmatched by the U.S. Navy's nearby warships, hope to evade capture by returning to lawless Somalia.
A U.S. official also said Saturday the pirates fired on U.S. sailors as they tried to reach the lifeboat where Phillips is being held, CNN reported.
The gunfire reportedly forced the sailors back to the USS Bainbridge.
Attorney General Eric Holder said this past week that the Justice Department had not seen a case of piracy against a U.S. ship in a very long time. But authorities have prepared for such an event as the threat of piracy along the African coast has risen.
"If there were ever a U.S. victim of one of these attacks or a U.S. shipping line that were a victim, our Justice Department has said that it would favorably consider prosecuting such apprehended pirates," Stephen Mull, the acting undersecretary of state for international security and arms control, told Congress last month.
Under U.S. law, crimes aboard U.S. ships or against U.S. citizens can be prosecuted in U.S. courts, even when they occur in international waters.
The FBI investigation is being run out of New York because the office there oversees cases involving U.S. citizens in Africa. Other field offices take the lead depending on where in the world the crime occurs.
The FBI has a legal attache at the U.S. Embassy in Kenya and has agents elsewhere in Africa to assist the investigation.
If the pirates make it safely to Somalia, it will impair the FBI's case because the U.S. does not have an extradition treaty with Somalia.
Justice Department spokesman Dean Boyd would not discuss the investigation.
"We all hope to resolve this situation as quickly and safely as possible," he said.
Maersk Shipping's President Reinhart praised the Navy and the FBI for their handling of the case.
"Every governmental agency has been brilliant and working tirelessly to help with the rescue of our crew, their safe return, and also the efforts to negotiate the release of Richard Phillips," he said.
The Associated Press contributed to this report.