Lung and adrenal lesions found in dead bottlenose dolphins stranded along the Gulf of Mexico between June 2010 and December 2012 are consistent with the types of damage that marine mammals sustain from exposure to petroleum products after an oil spill, according to a new study published on Wednesday by researchers from the National Oceanic and Atmospheric Administration.

The findings are the latest results from the Deepwater Horizon National Resource Damage Assessment, an ongoing investigation by NOAA into the spill, the largest offshore oil spill in United States history. Combined with previous studies by the agency, this paper provides additional support to a link between the Deepwater Horizon oil spill in 2010 and mass dolphin deaths in Alabama, Louisiana and Mississippi.

“The evidence to date indicates that the Deepwater Horizon oil spill caused the adrenal and lung lesions that contributed to the deaths of this unusual mortality event,” said Stephanie Venn-Watson, a researcher with the National Marine Mammal Foundation who was the lead author of the report. “We reached that conclusion based on the accumulation of our studies including this paper,” she added.

The researchers analyzed tissue samples collected from 46 dolphins, shortly after they died, in the area affected by the spill. They then compared them with samples from 106 dolphins that had died at different times from the spill and in other regions, including in Florida, North Carolina, South Carolina and Texas.