There is rising concern over the fate of Capt Phillips
Somali elders have launched a fresh attempt to resolve the standoff between the US navy and pirates holding an American captain hostage in a lifeboat.
Somali sources say a group of elders have taken to sea to arrange safe passage for the hostage takers.
The pirates have warned the US navy, which has warships and a helicopter in sight of the boat, against trying to rescue Capt Richard Phillips by force.
The FBI are questioning crew from Capt Phillips' ship, now docked in Kenya.
The container ship, which arrived in the port of Mombasa on Saturday evening, is being treated as a crime scene.
Crew members have hailed Capt Phillips' bravery, saying he offered himself as a hostage in order to save them when the Maersk Alabama was attacked on Wednesday.
The captain is now being held on a lifeboat said to be drifting about 30-45km (20 and 30 miles) off the Somali coast.
Reports from Maersk Line Ltd., the company which owns the ship, said the US Navy had "sight contact" with Capt Phillips earlier in the day.
Several warships and a helicopter are following the lifeboat's progress. Pirate sources were quoted by Reuters news agency as saying the helicopter was dropping supplies on the boat.
In a separate development, four French citizens including a three-year-old boy whose yacht was seized by pirates have returned to Paris after being freed by French troops on Friday.
The yacht's owner, Florent Lemacon, was killed during the operation along with two pirates.
A US military official said that on Saturday the four pirates guarding him fired shots at a small navy vessel which had approached, possibly to conduct reconnaissance.
No-one was hurt and the navy vessel turned away without returning fire, an unnamed US official told the Associated Press news agency.
MAJOR PIRATE INCIDENTS
Ukrainian ship MV Faina seized on 25 September 2008, held until 5 February 2009
Saudi tanker Sirius Star held for two months from November 2008; a $3m ransom was negotiated
At least 15 pirate attacks reported to International Maritime Bureau during March 2009
The 32,500-tonnSources at the ship's owne Malaspina Castle, UK-owned but operated by Italians, seized on 6 April 2009.
In the latest attempt to end the stand-off, elders said to be related to the pirates set sail from the northern Somali town of Eyl. US military officials confirmed fresh negotiations were under way.
The BBC's Jonah Fisher in Mombasa says the main stumbling block is the pirates' demand to be allowed to return to land before returning the hostage.
Earlier talks failed when US officials insisted on the pirates' arrest, the New York Times newspaper says, quoting unnamed Somali officials.
Abdi Garad, a Somali pirate commander, told AFP news agency on Saturday that there was concern the Americans were "planning rescue tricks like the French commandos did".
French commandos stormed a yacht on Friday to free hostages, but one captive was killed during the operation.
Also on Saturday, pirates hijacked a tugboat in the Gulf of Aden. The Buccaneer has 16 crew members on board, 10 of them Italians.
The Buccaneer was towing barges when it was seized
The crew, which also includes five Romanians and a Croat, are said to have been unharmed.
Another vessel, sailing under the Turkish flag, escaped when its crew used water hoses to repel the pirates who had fired a rocket-propelled grenade into the captain's cabin.
A piracy expert said the hijackings did not appear to be related to the attack on the Alabama Maersk.
"This is just the Somali pirate machine in full flow," Graeme Gibbon-Brooks, founder of Dryad Maritime Intelligence Ltd, told AP.