Scientists say they have first proof oil plumes beneath Gulf's surface came from BP spill

Researchers in Florida say they have the first scientific proof that two plumes of oil beneath the surface of the Gulf of Mexico came from BP's broken well.

University of South Florida scientists said Friday they linked the oil to BP's well based on chemical tests of two plumes discovered in late May. BP initially denied the plumes even existed.

Federal researchers say concentrations of underwater oil doubled last month over what they were in May.

Figuring out the oil's source is pivotal as the government assesses the environmental damage caused by the massive spill and how much BP will have to pay for it.

(This version corrects that federal researchers say the plumes were twice as concentrated last month as they were in May, not that the concentrations have doubled since last month.)