Congolese authorities are carrying out Ebola and cholera screening for all 255 passengers aboard a boat intercepted on the Congo River.

The Yingfeng 2 - operated by a Chinese company - was halted near Bende Bende port, some 65km (40 miles) upstream from the capital, Kinshasa.

Health Minister Roger Kamba said screening was being carried out as a precautionary measure after a passenger with fever and diarrhoea, who had got off at an earlier stop, had died in hospital. A further two adults, a three-year-old child and a newborn have also died.

Teams from the health ministry and the World Health Organization (WHO) have boarded the boat and set up a mobile lab to conduct tests.

"For now, no-one has tested positive, and it is likely no one will be positive after 21 days of incubation has elapsed," Kamba told reporters.

The vessel departed Kisangani, DR Congo's third largest city, about two weeks ago, the BBC understands.

Ebola cases have recently been reported there, with at least four deaths.

Kamba added there had been no Ebola cases in Mongala Province - where the passenger who died disembarked - contrary to earlier reports.

The boat travelled more than 1,700km downstream towards Kinshasa before being intercepted.

Security services have been instructed to quarantine the Yingfeng  2 offshore in line with WHO standards to prevent potential spread of the virus into the capital. Public health teams remain on standby to act once the boat is secured.

The country has been grappling with its 17th Ebola outbreak since May 15. It has been caused by the rare Bundibugyo species of the virus, which had not been seen for more than a decade.

There are no drug treatments that specifically target Bundibugyo, nor does it have a vaccine, although the first human trials for one are currently under way in the UK.

Three months since the outbreak was declared, infections and deaths continue to rise.

Official figures show that there have been 3,973 confirmed cases and 1,801 deaths - the second deadliest Ebola outbreak.

There are currently more than 17,000 people under monitoring after coming into contact with Ebola cases, 674 patients in isolation or treatment across five provinces, and 776 recoveries, according to authorities.

In Kinshasa, preparations for a possible Bundibugyo response are intensifying, with surveillance and rapid-response capacity being reinforced at Maluku, the city's main entry point.

Officials have reiterated that the measures are precautionary, but they underline the gravity of the situation.