Brazil’s biggest and most ambitious expedition in decades to contact a voluntarily isolated indigenous tribe has been declared a success after venturing deep into remote and inaccessible Amazon jungle.

The rare, high-risk expedition aimed to prevent potential conflict between tribal groups in a vast and remote reserve near Brazil’s Peruvian border.

Thirty people, including officials from its indigenous agency Funai, indigenous people from four local tribes, a doctor and medical officials, successfully contacted and vaccinated 34 people from the Korubo tribe.

“We had some incredible moments which we will never forget. Our hope is that [the Korubos’] lives are good from here on,” said expedition leader Bruno Pereira, head of the department of isolated and recently contacted indigenous at Funai.

The Funai expedition made contact with group of 34 Korubo people, including eight men, six women, children and three babies, Funai said in a statement. The group lives by hunting and plantations of crops like banana, corn and manioc.

The expedition set off along the Coari river in the Javari Valley, a remote and inaccessible indigenous reserve the size of Austria, on 3 March. The densely forested reserve of nearly 31,000 sq miles – home to about 6,000 indigenous people from eight tribes and 16 voluntarily isolated groups – is only accessible by boat or helicopter.

Among its 30 members were six Korubo people who had previously made contact. They searched the forest for over a week, finding the isolated group’s village on 13 March but not the tribespeople. On 19 March, Xuxu Korubo, himself only contacted in 2015, and others met two men from the isolated group out hunting – both Xuxu’s brothers. When the whole group was together he found a third brother and others met relatives they had not seen in years.

“It was extremely emotional,” said Pereira. “They were hugging, crying a lot.”

One member of the isolated group had malaria but has been treated and they have all now been vaccinated for viruses such as measles and flu that can prove deadly to indigenous people with no immunity. “They’re well, they’re strong,” Pereira said.

Korubo people get their first look at a laptop computer. Photograph: Courtesy Funai

Last year Guardian reporters joined an expedition monitoring isolated groups led by Pereira in the same area that included some of the indigenous people involved in this latest mission, as well Korubo tribesmen. Reporters interviewed Xuxu – who voiced his concern then over three brothers still living isolated in the forest and the threats they faced from armed commercial fishing gangs who invade the reserve.

The Korubo are a proud and warlike tribe who hunt with blowpipes and long wooden clubs. They have a long history of resisting invaders, and the first Korubo group was first contacted in 1996.

Another isolated Korubo group had a long-running dispute over territory with a neighbouring tribe, the Matis – who wear western clothes, hunt with guns and were contacted in 1975. The dispute between the tribes turned violent in 2014. Two Matis were killed by Korubo tribespeople and nine to 10 Korubo killed later in a counter-attack by Matis armed with shotguns.

Funai intervened, and those isolated Korubo – including Xuxu – went to live with contacted Korubo living in riverside villages. But another group remained isolated in the forest – and it was these that the expedition set out to contact.

Pereira said it was because tensions have continued to simmer in the area, with Matis complaining that isolated Korubo were appearing near their villages and Korubo anxious to contact relatives in the isolated group. Funai decided to intervene to avoid “a new confrontation”, Pereira said before setting off in February, adding his concern that non-contacted Korubo could be exposed to viruses the Matis have that they lack immunity to.

The expedition found thriving plantations with corn, banana and manioc used by the isolated group, who made a temporary camp as their relatives tried to convince them not to visit Matis villages and take axes and other tools.

“We let the relatives do the talking, we don’t want to be invasive. It is an intermediary relationship,” said Pereira. “They are suspicious of us, they don’t like our smell, the smell of soap.”

Pereira said the operation did not mean the Funai policy of not contacting isolated groups had changed. “It is important that the policy of isolation continues, of containment. We carried out a delicate operation for their safety. We believe that if we hadn’t done there could have been a new conflict,” he said.