British environmental journalist Dom Phillips and Indigenous Brazilian activist Bruno Araújo Pereira have disappeared in a remote part of the Amazon after recent threats were made against them for their work with a group monitoring illegal mining and fishing.

Phillips, a freelance journalist for The Guardian who has written extensively on threats of climate change to Brazil’s environment and the Indigenous communities of the Amazon, has been traveling in the region reporting for a new book. Phillips was accompanied by Pereira, a former government official now working with an Indigenous organization called Univaja that protects uncontacted tribes and patrols in the Vale Do Javari reserve in Amazonas, near Peru.

Phillips and Pereira were last seen following a planned meeting along the Itaquaí River early Sunday morning, but did not return as expected in their boat to the city Atalaia del Norte, the entry point to the reserve, Univaja said in a statement Monday. Activists and journalists criticized Brazilian authorities for their sluggish response in joining Indigenous activists searching the area, which is marked by a tangle of complicated waterways that can be slow to traverse by boat. Following the criticism, the Brazilian Navy said it would deploy a helicopter Tuesday.

Amazonas in recent decades has been plagued by violence as deforestation has especially increased under President Jair Bolsonaro, whose government has greatly weakened environmental protections.

“Under the Bolsonaro government the pressure [on activists to cease monitoring illegal activities] has increased even more because the invaders felt empowered and became more aggressive,” Beto Marubo, an Indigenous leader in the region, said, calling for an “urgent search mission” with “no time to lose.” “These are systematically organised gangs that are plundering the Javari region. They are veritable gangs and they are very violent.” (The GuardianNew York Times $)