A massive search-and-rescue operation is under way after a ferry sank ⁠off the coast of Guyana in South America ⁠late on Saturday, in what has been described by officials as one of the country’s worst maritime disasters.

Authorities launched a criminal investigation after a government official said the captain and a crew member of the ferry allegedly tested positive for marijuana and the vessel’s passenger manifest was found to be inaccurate.

Two people have been confirmed dead in the accident.

Authorities had previously said that there were 116 passengers and 17 crew members on board – as stated on the ship’s manifest – and confirmed that there was no mechanical problem and the vessel had been operating within its legal limits.

But speaking at a press conference alongside the country’s prime minister late on Sunday, Juan Edghill, Guyana’s minister of public works, told reporters the manifest was wrong after it was discovered that only 35 of 67 people rescued so far were on the passenger list.

The captain and the first engineer, both of whom allegedly tested positive for cannabis, are now in police custody.

“I am outraged. We are talking about operational breaches; people will be dealt with,” Edghill said at a press conference in Georgetown on Sunday night.

The ferry MV Barima left Georgetown, the capital of the English-speaking South American country, on Saturday at about 3.15pm for Port Kaituma, located in the oil-rich Essequibo region and just off the border with Venezuela.

A distress call was received shortly after 11pm, prompting an emergency response involving the Guyana Defence Force Coast Guard and Air Corps, private aircraft, fishing vessels and civilian volunteers.

Edghill had previously said the MV Barima was certified to carry 397 passengers and 284 tonnes of cargo. The ship was equipped with 250 lifejackets, two lifeboats and six inflatable rafts, Edghill had said.

The country’s prime minister Mark Phillips described the news that the manifest was incorrect as “deeply concerning and shocking”.

“The government has ordered an urgent and comprehensive investigation involving the Guyana Police Force, the Guyana Defence Force, the Maritime Administration Department, and other technical maritime experts,” Phillips said, adding that the accuracy of the passenger manifest and compliance with maritime safety regulations would be examined.

He added: “Let me be absolutely clear: where negligence, misconduct, or criminal wrongdoing is established, those responsible will face the full force of the law..”

Earlier on Sunday, Phillips said the search and rescue coordination centre had expanded the search area from 400 sq km (154 sq miles) to 1,070 sq km, with additional aircraft and vessels deployed alongside local fisherfolk familiar with the waters.

As the rescue effort continued, survivors recounted the moments when the ferry overturned in darkness.

Adam Matabheek, who was travelling with his wife, brother, sister-in-law and three young nieces and nephews, said he noticed the vessel leaning several hours before it capsized.

“We dismissed it as rough water and went to sleep,” he said.

Moments later, the vessel rolled over. “I ended up in the water,” he recalled, saying he managed to grab a lifejacket before drifting through the night.

His wife, Carlita Matabheek, who cannot swim, said she became trapped inside the overturned vessel before a lifejacket fell within her reach. “I started to pray,” she said.

After calling repeatedly for her husband in the darkness, she felt someone tugging at her hair. “It was Adam,” she said.

The couple and Adam’s younger brother, Nathaniel, spent the night drifting in the sea until rescuers found them after daybreak.

“God cleared the skies and saved us,” Carlita said.

Their relief, however, was overshadowed by tragedy.

Nathaniel’s wife, Rachel Welch, and their three children – Nathaniel Jr., 8, Natalia, 5, and Ezekiel, 3 – remain among the missing. According to the family, Rachel was thrown from her hammock as the ferry capsized and tried desperately to reach her children before they disappeared into the water.

Another survivor, Loureen Singh, a trader who regularly travels to Port Kaituma to sell clothing, survived by holding on to the same lifejacket as Carlita after telling her she could swim “a little”.

Carlita urged her: “Hold on to me.”

The two women remained together throughout the night until they were rescued.

Guyana’s international and regional partners have offered assistance in the search and rescue.