(CNN) -- Government investigators found no proof substantiating reports that miners massacred members of an indigenous community in the Venezuelan Amazon, officials said.
But activists and indigenous groups said Monday that the government was too swift in denying that dozens of Yanomami Indians died in an attack that reportedly occurred in July, and that was the subject of a call for action last week by a Yanomami organization and other groups.
"It's far too early for the Venezuelan government to be denying this massacre took place," said Chloe Corbin, a spokeswoman for London-based Survival International.
Allegations of the massacre trickled out of a remote region along the Brazil-Venezuela border, where unauthorized Brazilian gold miners have long clashed with indigenous groups.
The Yanomami, who live in both nations, are considered the largest indigenous group in the Americas that remains largely untouched by advances in the outside world.
Venezuelan officials said last Wednesday they were investigating reports of an attack. On Saturday, a top official said visits to the region revealed that reports about the alleged massacre were false.
"We can tell the country that there is no evidence of any deaths, nor any evidence of homes burned down in the supposed massacre of 80 of our Yanomami brothers," Nicia Maldonado, Venezuela's minister of tribal people, told state-run VTV.
On Sunday, the South American country's interior minister described the allegations as "false news," accusing private media companies and members of the opposition of spreading the report.
In a Twitter post, Interior Minister Tareck El Aissami said government investigators had visited all of the Yanomami communities and "all are well."
But a group of organizations representing indigenous people and communities in the Amazon said the investigators hadn't visited the area where the attack is reported to have taken place.
For that reason, the groups said in a statement published on the website of the Venezuelan human rights organization Provea, the authorities can't "say that no evidence proving the alleged massacre has been found."
They urged the government to continue the investigation and to go as far as site of the settlement that was reportedly attacked.
The area is a five-hour helicopter ride, or 15 days on foot, from Puerto Ayacucho, the main Venezuelan city in the Amazon, the government said.
Survival International, which advocates tribal peoples' rights worldwide, said in a written statement that the government officials' comments are "not unusual in these circumstances and should be ignored."
"There is more that needs to be done on the ground to get to the bottom of this reported massacre and find out how many people were affected by it," Corbin said.
Indians told members of a neighboring Yanomami community that they saw burned bodies and bones in the area where the attack allegedly occurred, according to Survival International, which had contacted local representatives but had not spoken directly with any witnesses of the alleged attack.
Of about 80 Yanomami people who lived in the Irotatheri community, only three survivors had been found, according to a declaration published on Survival International's website, purportedly from indigenous organizations.
In recent years, the Yanomami tribe has been under increasing pressure as miners illegally entered their land in the search of profits.
Miners in Brazil have transmitted diseases such as malaria and flu to the Yanomami, who have little resistance to such diseases, observers say.
CNN's Catherine E. Shoichet and Marilia Brocchetto contributed to this report.