New Orleans, Louisiana (CNN) -- If all goes as planned, the "bottom kill" operation to permanently plug the ruptured underwater well in the Gulf of Mexico should be completed by the week after Labor Day, Thad Allen, the government's point man for the oil disaster, told CNN Thursday.
In the last 48 hours, a sequence of actions has been agreed upon, Allen told CNN's "American Morning." Those include flushing out the current blowout preventer, looking for material that may cause a problem, then putting a new blowout preventer on and conducting the "bottom kill" operation.
"This will ensure that we can withstand any pressures that may be generated," Allen said. "If all that lines up, we should be looking at the week after Labor Day."
Later Thursday, Allen said he had authorized BP, the oil company that operated the sunken well and is responsible for cleanup, to replace the existing blowout preventer with a new one ahead of the "bottom kill."
The oil disaster began April 20, when the Deepwater Horizon oil rig exploded, killing 11 workers, and later sank. The government estimates some 4.9 million barrels of oil gushed into the Gulf. The well was capped July 15, stopping the flow of oil, and a "static kill" operation two weeks ago further plugged it with cement and mud from above.
The "bottom kill" operation is a permanent fix, in which the well will be intercepted by a relief well and the ruptured well will be plugged from below.
The replacement of the blowout preventer means the well's old blowout preventer will be retrieved and brought to the surface, where it could provide clues about what caused the April explosion.
Allen told reporters Thursday that officials are in the midst of conducting an ambient pressure test to determine whether the pressure in the top of the well matches the pressure outside the well. That test is expected to be complete Saturday morning. If no anomalies are detected, BP will conduct a "fishing experiment" to try to pull out the drill pipe through the top of the well, Allen said. If both steps are successful, he will then have to issue another go-ahead to remove the existing blowout preventer and replace it with a new one.
The early-September timeline, he said, is "conditions-based." He denied that the bottom kill was being delayed, but said it was going forward with "very deliberate consideration."
Asked about a letter dated Wednesday from Transocean that accused BP of withholding "key information about the well," Allen told reporters the communication was between the two companies. BP was leasing the rig from Transocean, whose crew operated the offshore platform.
Transocean attorneys write in the seven-page letter that it is "at least the seventh request" for information, including real-time data collected by BP, documents, logs, cementing and operational reports and seismic data. Such information, the letter says, is "critical to identifying the cause of the tragic loss of 11 lives and the pollution of the Gulf of Mexico."
"Despite Transocean's prompt and transparent production of information requested by BP, BP has continued to demonstrate its unwillingness, if not an outright refusal, to deliver even the most basic information to Transocean," said the letter, signed by Steven Roberts, acting co-general counsel for Transocean.
"We're disappointed that Transocean has opted to write a letter with misguided assertions, including the assertions that BP is withholding evidence concerning the April 20th accident and the resulting oil spill," BP spokesman John Curry said in a statement.
Meanwhile, a House hearing was being held Thursday on the safety of Gulf seafood in the aftermath of the disaster. Scientists, professors and members of seafood organizations were set to testify at the hearing before the House Committee on Energy and Commerce. However, committee chairman Rep. Ed Markey, D-Massachusetts, was the sole lawmaker in attendance as the hearing got under way.
Markey noted that some people have gone away for the summer, but said the oil has not gone away, and neither has the attention focused on the matter.
Tests on animals, including shrimp, crab and oysters, showed essentially the same level of contamination as before the oil disaster, testified Donald Kraemer, acting deputy director of the Food and Drug Administration's Office of Food Safety. Levels are well below the area of concern, he said. In addition, studies continue to show that dispersants used on the oil are not accumulating in seafood.
Allen told reporters that seafood coming from reopened Gulf fishing waters is safe to eat.
Jane Lubchenco, director of the National Oceanic and Atmospheric Administration, echoed Allen's comments about Gulf seafood, saying that where water may still be tainted, no fishing is allowed.
"Twenty-two percent of federal waters in the Gulf remain closed because we have not yet determined it's safe" to eat seafood from there, Lubchenco said.
But there are some that are still skeptical about the safety of seafood. Acy Cooper, a commercial fisherman and vice president of the Louisiana Shrimpers Association, disputed claims there is no oil on the ocean floor.
"We know it's there," he testified at the House hearing, referring to the oil. "... BP, if we let them leave now, we're going to be in a lot of trouble."
He said a few places are indeed clean of oil, and fishermen stay away from areas that are not clean because "we want to make sure what we put on the market is good ... we get somebody sick, it's going to come back to us."
He said in a typical season, he usually catches 10,000 pounds of shrimp. This year, he's caught 500 pounds.
"How am I going to survive?" he said. "They say the oil's gone, it's not gone. You stir the bottom up and oil comes up."
This week, a major environmental watchdog group called for more stringent testing of Gulf seafood, where the fall shrimping season began this week.
The Natural Resources Defense Council released a statement saying it sent letters to the Food and Drug Administration and NOAA, co-signed by almost two dozen Gulf Coast groups.
"With the opening of shrimping season and near-daily reopening of fishing areas, seafood safety is a major issue right now," Dr. Gina Solomon, a senior scientist with the Natural Resources Defense Council, said in the statement. "The government needs to show it is putting strong safety criteria and testing standards in place to ensure that the seafood from the Gulf will be safe to eat in the months and years to come."
Asked Thursday about any toxicity that remains from the use of dispersants, Allen noted that the Environmental Protection Agency recently found oil mixed with dispersants was no more toxic than the oil itself.
"I don't think there's an issue with the dispersants," Allen said. "Now, there's a larger issue from a public standpoint on how much we want to use in the future, and we want to look at that moving forward."
Meanwhile, top administration officials toured the Delta National Wildlife Refuge in Louisiana and reiterated their intention to see the Gulf restoration through, and to ensure BP does its part.
"In so many ways, our work has just begun," said Secretary of Interior Ken Salazar.
CNN's Paul Courson and Vivian Kuo contributed to this report.