Paraguay suspended a British scientific expedition into the remote Chaco woodlands after indigenous rights groups raised concerns over the welfare of protected tribes in the region.
Sponsored by Britain's Natural History Museum, the 45-member British-Paraguayan expedition planned to conduct a month-long survey of animal and plant life in the sprawling savanna 800 kilometers (500 miles) north of Asuncion, the ministry said in a statement.
The decision to suspend it followed "last minute" concerns raised by indigenous rights groups including Iniciativa Amotocodie, and recommendations by the Washington-based Inter-American Human Rights Commission, the environment ministry said.
"The massive presence of about 60 researchers in the land inhabited by the Ayoreo tribal groups in the remote, northern reaches of Chaco... poses significant risks to their lives and territory," Amotocodie said in a statement.
The rights groups argued that since the tribes have had very little contact with the outside world they are at risk of contracting diseases that in some cases could prove fatal.
Explore further: Pact with devil? California farmers use oil firms' water