NEW ORLEANS (AP) — While BP is capturing more oil from its blown-out well with every passing day, scientists on a team analyzing the flow said Tuesday that the amount of crude still escaping into the Gulf of Mexico may be considerably greater than what the government and the company have claimed.

Their assertions — combined with BP’s rush to build a bigger cap and its apparent difficulty in immediately processing all the oil being collected — have only added to the impression that the company is still floundering in dealing with the catastrophe.

The cap that was put on the ruptured well last week collected about 620,000 gallons of oil on Monday and another 330,000 from midnight to noon on Tuesday and funneled it to a ship at the surface, said Coast Guard Adm. Thad Allen, the government’s point man on the crisis. That would mean the cap is capturing better than half of the oil, based on the government’s estimate that around 600,000 to 1.2 million gallons a day are leaking from the bottom of the sea.

The undersea efforts came as BP Chief Operating Officer Doug Suttles struck an upbeat tone about the anticipated progress of the oil containment in the next week. Suttles told The Associated Press in a stop in Alabama that the arrival of a second vessel in the coming days to help pump the oil from the deepwater gusher could help engineers make even more progress, even as others continued to criticize BP over its handling of the disaster.

A team of researchers and government officials assembled by the Coast Guard and run by the director of the U.S. Geological Survey is studying the flow rate and hopes to present its latest findings in the coming days on what is already the biggest oil spill in U.S. history.

In an interview with The Associated Press, team member and Purdue University engineering professor Steve Wereley said it was a “reasonable conclusion” but not the team’s final one to say that the daily flow rate is, in fact, somewhere between 798,000 gallons and 1.8 million gallons.

“BP is claiming they’re capturing the majority of the flow, which I think is going to be proven wrong in short order,” Wereley said. “Why don’t they show the American public the before-and-after shots?”

He added: “It’s strictly an estimation, and they are portraying it as fact.”

Other members of the team also told AP they expect their findings to show higher numbers than the current government estimate, but they weren’t ready to say how much higher.

To install the containment device snugly, BP engineers had to cut away the twisted and broken well pipe. That increased the flow of oil, similar to what happens when a kink is removed from a garden hose. BP and others warned that would happen, and the government said the increase amounted to about 20 percent.

Asked about the containment effort and the uncertainties in estimating how much oil is escaping, Allen said: “I have never said this is going well. We’re throwing everything we’ve got.”

Paul Bommer, a University of Texas petroleum and geosystems engineering professor and member of the flow rate team, said cap seems to have made a “dent” in reducing the flow, but there is still a lot of oil coming out. That seemed clear from the underwater “spillcam” video, which continued to show a big plume of gas and oil billowing into the water.

The current equipment collecting the oil being brought to the surface is believed to be nearing its daily processing capacity. BP said it will boost capacity by bringing in a floating platform it believes can process most of the flow, and believes the extra pumping power can help reduce the spill even more by early next week, when President Barack Obama is scheduled to make his fourth visit to the Gulf since the disaster began.

The company also said it will use a device that vaporizes and burns off oil while working to design a new cap that can capture more crude.

Suttles initially said that the spill should be reduced to a “relative trickle” by Monday or Tuesday. BP later sought to clarify the comments by saying that even though the company is optimistic it can make measurable progress in the next week in reducing the flow, it will take more time to reach the point that the spill amounts to a trickle.

In the seven weeks since the oil rig explosion that set off the catastrophe, BP has had to improvise at every turn. The most recent government estimates put the total amount of oil lost at 23.7 million to 51.5 million gallons.

“I think virtually everybody from BP to the state to the Coast Guard was caught flat-footed and did not expect a spill of this magnitude,” said Ed Overton, a professor of environmental sciences at Louisiana State University. “Everybody has been playing catch-up.”

When asked why BP did not have containment systems on standby in case of a leak, BP spokesman Robert Wine said there was no reason to think an accident on this scale was likely.

“It’s unprecedented,” he said. “That’s why these caps weren’t there before.”

Kenneth Arnold, an offshore drilling consultant and engineer, said the reason a bigger cap wasn’t installed first was that BP probably wanted to start with what it could do quickly, which he said makes sense. He said BP has been working several solutions all along in parallel and deploying them as they can.

“They haven’t been waiting for one to fail and then employing the next one,” Arnold said.

He added: “The idea you can wave your arm at this and come to a magical solution is just from someone who doesn’t understand the problem. We as a nation are used to instant gratification. There is a problem. We want someone to fix it tomorrow. Things are not always that easy.”

Some answers may emerge next week, when BP CEO Tony Hayward will make his first appearance before Congress to answer questions in what will probably be a heated session, given the anger directed at BP.

The debate over the flow rate came as workers in bulldozers piled sand 6 feet high along barrier islands bordering Louisiana to protect the environmentally fragile areas from the spill, which has already coated islands and pelican rookeries in thick, brown, sticky crude.

“This is finally something that can help,” fishing guide Dave Marino said of the sand barrier effort. “It looks like this is something that may work.”

Attempts to skim the oil progressed as well. Boats fanned out across the Gulf, dragging boom in their wake in an attempt to corral the oil. But it’s an enormous task.

In some spots, the oil is several inches thick and forms a brown taffy-like goo that sticks to everything it touches.

John Young, chairman of Louisiana’s Jefferson Parish Council, said additional equipment has been ordered and more dredgers will be moving into the area soon, along with barges that will help block the passes.

“It’s nice that BP has put up the money, but they need to ramp up not only the manpower but the equipment out there because we’re losing the battle,” Young said. “Unfortunately, we’re on day 50 and it’s too little too late, but I guess it’s better late than never.”

Meanwhile, researchers are beginning to obtain a clearer picture of the spill as they analyze water samples. For example, marine scientists found a 100-foot-thick layer of oil 1,300 feet below the surface about 45 miles from the well site. BP said in a written statement that while there is oil in the water, the findings so far do not support the existence of undersea plumes.

And officials in the Florida Panhandle are posting signs warning beachgoers not to swim or fish off a six-mile stretch of oil-fouled beaches near the Alabama state line — the first time such restrictions have been imposed in the state since the spill began.