(CNN) -- Here are the latest developments on the oil disaster in the Gulf of Mexico, which unfolded after the oil rig Deepwater Horizon exploded on April 20:
A delegation of four U.S. senators head to the heart of coastal Louisiana Friday to assess the damage caused by the nearly two-month-long BP oil disaster.
LaFource Parish President Charlotte Randolph accused Obama of using the Gulf Coast for political purposes. "I think he has an agenda and this is certainly working into his agenda," Randolph said Thursday. "Right now we are the poster children for alternative energy. He can point to us and say this is why we need to move on to alternative energy."
The flow of oil from the broken pipe in the Gulf of Mexico, before an insertion tube was placed inside and before it was cut on June 3, was estimated to be from 20,000 barrels per day to twice that figure, a federal scientist said Thursday.
Scientists want BP to allow more accurate flow measurement equipment to go down to the leak site when the company switches out the containment cap. Current estimates are made visually by studying video from the site.
BP will begin testing a second rig-based system to catch oil this weekend. It would catch an extra 10,000 barrels a day, bringing daily total recovery capacity to 28,000 barrels, said Ken Wells, BP's senior vice president for exploration and production.
Jordan Barab, deputy assistant secretary of labor for occupational safety and health, told the Senate Subcommittee on Employment and Workplace Safety that investigators are finding a lack of compliance during inspections of refineries.
The Deepwater Horizon catastrophe, experts said Thursday, highlights flaws in the blowout preventer, which is supposed to shut down an oil and gas well if something goes wrong.
Federal agencies responsible for monitoring the toll to wildlife reported Thursday that 473 oiled birds have been collected alive; 658 were dead. The report said 52 sea turtles have been collected alive; 279 were dead.
BP has collected about 73,300 barrels (about 3 million gallons) of oil since it placed a containment cap on its ruptured well, the company said.
The collected oil was transferred from the drilling ship Discover Enterprise to a second ship, the Massachusetts, BP said. The Massachusetts will transport the oil for discharge at an onshore terminal.
Federal and local officials complained at a key Senate governmental affairs subcommittee urged the establishment of a clearer command-and-control system to accelerate the decision-making process and the creation of a more definitive chain of accountability.
The National Oceanic and Atmospheric Administration predicts alongshore currents becoming more westward over the next few days. That should prevent the oil from moving east. But the agency said that coastal regions between Horn Island, Alabama, and Pensacola, Florida, may continue to see oil come ashore on beaches. To the west of the Mississippi Delta, oil still floating on the ocean could come ashore between Timbalier Bay and Southwest Pass.
Images of oil-soaked birds and turtles have prompted a surge in people wanting to volunteer to help in the cleanup and rehabilitation process, said Anna Keene, programs director at the conservation group Alabama Coastal Foundation.
Transocean, the world's largest offshore drilling company, has invoked a 19th-century American law to limit its liability to $26.76 million, a fraction of what the plaintiffs are likely to seek.
BP announced $25 million grants to Alabama, Florida and Mississippi.
Florida Attorney General Bill McCollum asked BP on Thursday to deposit $2.5 billion into an interest-earning escrow account so the state can be assured of its availability over the long-term recovery period.
BP has pledged to speed up its payment of claims to businesses affected by the oil disaster, said Tracy Wareing, a Federal Emergency Management Agency adviser to Homeland Security Secretary Janet Napolitano.
President Barack Obama will meet Wednesday with BP Chairman Carl-Henric Svanberg at the White House, a senior White House official told CNN Thursday.
Responsibility is a key question for families of the 11 oil rig workers who were killed and the 15 others who were injured in the April 20 explosion of the Deepwater Horizon. Many of them, who met Thursday with Obama, are suing BP and Transocean, the Swiss-based company that owns the drilling rig.
The Obama administration won't reconsider its moratorium on deepwater oil drilling "without knowing exactly what happened" to cause the oil disaster, White House spokesman Robert Gibbs said Thursday.
Some of the rig victims' families and Gulf politicians have objected to the moratorium.
Sen. Patty Murray, D-Washington, blasted BP on Thursday for failing to attend her subcommittee's hearing on oil and gas worker safety.
House Republican leader John Boehner mocked Congress on Thursday for holding multiple hearings on the disaster before experts have figured out how to stop the undersea gusher. He sarcastically called the packed hearing schedule "Congress at its best."
Obama will make another visit to the Gulf Coast next week to review efforts to contain and clean up the worst oil spill in U.S. history.
BP's top official, Tony Hayward, has been asked to appear at a hearing June 17 before the House Subcommittee on Oversight and Investigations.
Advocacy groups are planning a nationwide vigil this month.
Experts disagree over whether oil-soaked birds should be cleaned, with one saying only about 1 percent survive.
Work continued on the effort to drill a relief well 16,000 to 18,000 feet below the seafloor, described as the only surefire way to stop the oil from spewing into the Gulf. As of Thursday, BP said the drill for this relief well has reached 13,978 feet.