The bodies of at least 21 illegal immigrants have been discovered in an inflatable boat drifting in the Adriatic Sea between Albania and Italy, a Nato source in Albania said on Saturday.
Antonio Passara of the Nato office in Albania's capital Tirana said that 18 of the victims were men and three were women. Earlier reports said 14 people, including two children, had died in the tragedy.
The Italian navy in Rome said that one of its launches based in the Albanian port of Durres - a favourite jumping-off point for immigrants desperate to reach western Europe - had gone to the rescue of a vessel on Friday night.
One of the boat's occupants had raised the alarm by telephoning an Albanian television programme, officials said.
Initial reports said that at least 30 people may have been crammed on to the boat, which was shipping water. It was successfully towed to the island of Sazan, about 10 kilometres (6 miles) from the Albanian port of Vlora.
Officials said they were searching for a second boat that had disappeared in the same area.
Italian navy officer Ivano Bascheri said the launch had also rescued 11 survivors, all men aged between 18 and 30.
He said they were in an extremely bad state of health. All were being taken to the hospital at Vlora.
It was not clear how the occupants of the boat died.
Meanwhile, the Albanian authorities announced on Saturday that at least four top Albanian police officials had been arrested in connection with the tragedy.
Police spokesman Florian Serani said that among them was a leading anti-terrorist official from the northern town of Shkodar, from where the majority of the illegal immigrants are thought to have set out.
He said there were indications the four police had organised the immigrants' planned passage to Italy and were even the owners of the inflatable boat involved in the incident.
Serani said all could face murder charges. The immigrants are believed to have paid between 1,800 and 2,000 euros apiece for their journey to Italy.
Nato takes part in rescue operations led by Italian naval ships patrolling territorial waters between Italy and Albania.