The body of a Somali pirate who drowned after receiving a huge ransom has washed ashore with $153,000 (£100,000) in cash, while a spokesman for another group of pirates promised to soon free a Ukrainian arms ship.

Five pirates drowned on Friday when their small boat capsized after they received a reported $3m ransom for releasing a Saudi oil tanker. Local resident Omar Abdi Hassan said one of the bodies had been found on a beach near the coastal town of Harardhere and relatives were searching for the other four.

"One of them was discovered and they are still looking for the other ones. He had $153,000 in a plastic bag in his pocket," he said.

The US navy released photos of a parachute dropping a package on to the deck of the Sirius Star, and said the package was likely to be the ransom delivery.

Graeme Gibbon Brooks, managing director of the British company Dryad Maritime Intelligence Service, said the incident was unlikely to deter attacks.

"The loss or potential loss of the ransom means the pirates will be all the more keen to get the next ransom in," he said. "There are people lining up to be pirates."

The Sirius Star had been held near the Ukrainian cargo ship MV Faina, which was loaded with 33 Soviet-designed battle tanks and crates of small arms. The same day the Sirius Star was released, the family members of the Faina crew appealed for help, saying they were not kept informed about the negotiations or the state of their loved ones' health.

But a pirate spokesman said today that the 20 crew members on the MV Faina were doing well.

"The cargo is still there unharmed and the crew is healthy," Sugule Ali said. "Once the negotiations end in mutual understanding, the ship, its crew and the cargo as well will be released."

There have been several false alarms about the release of the MV Faina since it was seized in September. Ali said the pirates were still negotiating with the ship's owners.

"Nothing has changed from our previous demand of $20m ransom for the release of the ship, but as negotiations continue we are likely to reduce the amount," he said. He declined to give further details.

American warships have been closely monitoring the Faina amid fears that some of the weapons on board could be taken onshore and fall into the hands of Islamic insurgents.

The shaky Somali government is battling insurgents that the US state department says are linked to al-Qaida. But the situation is complicated by clan militias and rivalries within the Islamist movement.

Somalia has not had a functioning government since 1991 and its lawless coastline is a haven for pirates, who attacked 111 ships in the Gulf of Aden and kidnapped 42 of them last year alone. An international flotilla including US warships has been patrolling the area. The flotilla has stopped many attacks, but the area is too vast to keep all ships safe.