Is enough being done to protect the public from chemical pollutants? Watch "Toxic America," a special two-night investigative report with Dr. Sanjay Gupta, Wednesday and Thursday at 8 p.m. ET on CNN.

Washington (CNN) -- Rep. Edward Markey on Monday challenged the assertion by oil giant BP's chief executive that no underwater oil plumes have formed because of the Gulf of Mexico spill.

Markey, D-Massachusetts, said in a letter to BP that scientific evidence showed such plumes have formed, and he asked for BP CEO Tony Hayward to provide evidence to back up Hayward's claim Sunday that the oil had gone to the surface.

On Sunday, Markey, who heads the House Energy and Environment subcommittee, accused BP of issuing false statements about the spill.

"BP in this instance means 'Blind to Plumes,' " Markey said in a statement Monday. There was no immediate response from BP.

Full coverage of oil spill

In other developments, BP's latest plan to cap the undersea well has been modified to collect more crude and to prepare for a possible hurricane, the company said late Monday night.

Also, the federal government ordered another 1,200 square miles of the Gulf of Mexico closed to fishing Monday, extending the restricted zone off Louisiana toward the coasts of Alabama and Mississippi.

The latest order from the National Oceanographic and Atmospheric Administration means about 26 percent of the Gulf is closed to fishing, up only slightly from 25 percent last week. But it comes on the eve of the opening of the recreational fishing season for red snapper, a strong draw for sport fishing in the region.

The closure extends from north of Louisiana's Chandeleur Islands, east along the three-mile offshore border between federal waters and Alabama and Mississippi state waters to just west of Gulf Shores, Alabama. It follows NOAA forecasts that showed oil from the massive Deepwater Horizon spill spreading toward those states' coasts later this week.

"Closing fishing in these areas is a precautionary measure to ensure that seafood from the Gulf will remain safe for consumers," NOAA said in a statement announcing the decision.

The move is likely to be another blow to an already beleaguered fishing industry, which brings in billions of dollars to the Gulf states. Early studies have estimated the economic damage from the spill could run as high as $1.6 billion.

iReport: Track the oil spill

Markey's letter to BP said "the confirmation of the presence of large quantities of oil sub-surface could help to inform clean-up and response efforts, and it is vital that there is unfettered access to all relevant data or analysis."

The letter noted that University of South Florida researchers recently reported finding a 22-mile-long plume of dispersed oil.

In a separate letter Monday to BP, Markey called for complete transparency regarding video feeds of the company's underwater operations. BP is launching an effort to cut an opening to the leaking equipment so that a containment dome can be lowered on it.

"There cannot be any delay or gaps in our understanding of this situation, given that thousands of barrels of oil are spewing forth each day into the Gulf, with catastrophic long-term consequences," said Markey's letter to BP America head Lamar McKay, adding: "BP should not be controlling the view the American public has of this disaster in our ocean."

As the oil spill entered its 42nd day Monday, efforts to clean up coastal areas and develop a new plan of attack continued.

BP could try to cap a massive oil gusher again this week in an attempt to solve what the Obama administration has called "probably the biggest environmental disaster we've ever faced in this country."

All attempts at containing the crude gushing from BP's undersea well have failed, including a "top kill" approach on which many had pinned their hopes.

BP said Sunday that it would strengthen its efforts to stop the flow and protect the coastline.

"As far as I'm concerned, a cup of oil on the beach is a failure," Hayward said in Venice, Louisiana.

Hayward said he was sorry for the spill and the "massive disruption" it has caused the Gulf Coast.

"There's no one who wants this over more than I do. I would like my life back," Hayward said. But he said the company has about 30 aircraft searching for signs of oil and has moved more than 300 people to offshore "floatels" to speed up its response time.

Up to 19,000 barrels (798,000 gallons) of oil a day have been spewing out of the BP-owned undersea well since the late April sinking of the drill rig Deepwater Horizon.

BP, rig owner Transocean Ltd. and oilfield services company Halliburton have blamed each other for the disaster, which left 11 workers dead, but BP is responsible for cleanup under federal law.

"We're disappointed the oil is going to flow for a while, and we're going to redouble our efforts to keep it off the beaches," BP Managing Director Robert Dudley said on CNN's "State of the Union."

Glossary of oil terms

Dudley said the next effort will involve placing a custom-built cap to fit over a piece of equipment called the "lower marine riser package." The process will involve cutting the riser package to create a clean surface to cap, Dudley said, and warm water will be circulated around the cap to prevent the freezing that hindered a previous dome-cap effort.

If successful, the procedure will allow BP to collect most -- but not all -- of the oil spewing from the well. The long-term solution is the drilling of a relief well that will be in place by August.

"If we can contain the flow of the well between now and August and keep it out of the ocean, that's also a good outcome as well," Dudley said. "And then, if we can shut it off completely with a relief well, that's not a bad outcome compared to where we are today."

On Sunday, the Obama administration questioned BP's oil spill numbers.

Read more about numbers dispute

On NBC's "Meet the Press," Carol Browner, Obama's assistant on energy and climate change, said BP may have had an ulterior motive for underestimating the amount of oil leaking.

"BP has a financial interest in these numbers. They will pay a penalty based on the number of barrels per day," she said.

BP had originally said that about 5,000 barrels of oil per day were leaking.

The latest estimate, Browner said, is between 12,000 and 19,000 barrels per day.

More oil is leaking into the Gulf of Mexico than during any other spill in U.S. history, including the 1989 Exxon Valdez oil spill in Alaska, according to the government.