NEW ORLEANS, (AP) - A spokesman for BP PLC says the company needs more proof to support claims by scientists that huge plumes of oil are suspended underwater in the Gulf of Mexico.

CEO Tony Hayward said Sunday there was "no evidence" of the plumes and that all the oil from the spill was floating to the surface. Spokesman Graham MacEwen said Tuesday that BP is awaiting analysis of water samples taken in the Gulf before making a final determination.

Since an April 20 blowout aboard the Deepwater Horizon drilling platform, researchers from universities in Florida, Georgia, Louisiana and Mississippi have reported plumes.

Rep. Edward Markey, a Democrat from Massachusetts, has asked BP to back up Hayward's claim that they do not exist.