The National Oceanic and Atmospheric Administration, which earlier this month confirmed the existence of deepwater oil plumes in the Gulf, has now released a report that concludes those plumes are from BP's well in the Gulf, citing a "preponderance of evidence" gathered from four separate sampling cruises. (I read about the report in the Miami Herald.) BP execs had initially denied there were underwater plumes. After government scientists confirmed the plumes, BP refused to hand over samples that would have clarified whether the underwater oil was in fact from the spill. 

From the government's report [PDF], which was released yesterday:

The preponderance of evidence based on careful examination of the results from these four different cruises leads us to conclude that DWH-MC252 oil exists in subsurface waters near the well site in addition to the oil observed at the sea surface and that this oil appears to be chemically dispersed. While no chemical "fingerprinting" of samples was conducted to conclusively determine origin, the proximity to the well site and the following analyses support this conclusion.

While the ecological effects of dispersed oil are still unknown, it should also be noted that the latest findings show oil at concentrations of about 1 to 2 parts per million--higher concentrations than that of previous sampling, which had found concentrations of less than 0.5 ppm.

Last month, NOAA described the plumes as "very low concentrations" of oil, and when BP's Doug Suttles was asked about them on NBC's Today Show, he sidestepped the question, saying "we haven't found any large concentrations of oil under the sea," and "it may be down to how you define what a plume is."

It's not clear from the Miami Herald's story, or the government's report, whether BP has shared the samples. I've called BP for a comment, and will update if they respond. I'm also contacting scientists who've been studying the plumes.