Heavy rainfall is threatening to impede the ongoing search for two individuals still missing in a flooded cave system in Laos, following the successful rescue of five others who had been trapped underground for over a week.

Finnish diver Mikko Paasi, among the first international rescuers to arrive at the scene, reported that rainwater had filled the cave up to its second chamber, preventing divers from entering until pumping operations could significantly lower the water level.

The seven villagers reportedly ventured into the cave last week in search of valuable minerals, only to be caught by a sudden flash flood that blocked their exit. One man managed to get out just in time and alert authorities.

Rescue teams from Laos and neighbouring Thailand have been collaborating intensely over the past week at the rugged site in Xaisomboun province, about 120km north of the capital Vientiane. They have been joined by expert divers from Finland, Malaysia, Japan, Indonesia, France, and Australia. Several of the rescuers were also involved in the complex 2018 cave rescue in northern Thailand which saw 12 schoolboys and their football coach safely extracted from a flooded cavern.

The five rescued men are currently receiving treatment at a local hospital and are reported to be in good health, according to Malaysian diver Lee Kian Lie, who is participating in the operation.

"We interviewed them about how the deeper part of the cave looks like. We will continue to search based on the information we have, and perhaps we will be able to get to the other two," he stated on Sunday.

Rescuers have so far navigated more than 200 metres into the cave, discovering five distinct chambers within the system. The five individuals rescued were located in the fifth chamber. Mr Paasi revealed that the survivors mentioned a narrow crack in this fifth chamber, which could potentially serve as a passage to a deeper section of the cave.

"This was the only place that we haven’t checked in the mine, where the two lost miners could still be," he said during a video interview. "Now there’s a theory that, through that small crack, it still continues, and there’s a sixth chamber, which gives us hope now that, if we could penetrate that small restriction, we might be able to reach the sixth chamber and then see what is there."

The five individuals, identified by their first names as Khamla, Mued, Ee, Ing, and Laen, were initially discovered on Wednesday. The first man was safely evacuated on Friday, guided through a narrow, flooded passage by an expert diver.

The remaining four exited the cave on Saturday after water levels receded sufficiently for them to walk out unaided, rescuers confirmed.

Videos shared online by rescuers on Saturday captured emotional scenes as the men emerged one by one from the cave. Some collapsed at the entrance, embraced by a group of workers who wept with joy. Subsequent footage showed them lying on stretchers, wrapped in foil blankets and fitted with oxygen masks, before being transported away from the site.