Brazilian officials have on Wednesday refused the state-run Petrobras environmental permission to conduct exploratory drilling at the Amazon River's mouth. 

The Petrobras project has "worrying inconsistencies for safe operation" in an area of high socio-environmental vulnerability, according to the government's environmental regulator Ibama.

The proposed drilling site is 180 kilometers (110 miles) off the coast of Amapa state, near French Guiana. 

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Ibama highlighted "deficiencies" in the project's impact assessment last month, including the preservation of wildlife in the event of an accident and the communication strategy with surrounding Indigenous villages. 

According to the materials, there would be a "probable loss of impacted biodiversity in the case of accidents involving oil spills." 

Ibama rejected a license to French oil major Total for drilling activity in the region in 2018 on similar grounds. 

Environmentalists have been against the crude oil extraction efforts in the Amazon River and the Atlantic Ocean, warning that they may endanger a freshwater barrier reef discovered there in 2016. 

The environmental group Observatorio do Clima applauded the Petrobas licensing decision, releasing a statement saying that Ibama "is protecting a virtually unknown ecosystem."