A U.S. congressman said he will launch a formal inquiry Friday into how much oil is gushing into the Gulf of Mexico after learning of independent estimates that are significantly higher than the amount BP officials have provided.

Rep. Edward Markey, a Democrat from Massachusetts, said he will send a letter to BP and ask for more details from federal agencies about the methods they are using to analyze the oil leak. Markey, who chairs a congressional subcommittee on energy and the environment, said miscalculating the spill’s volume may be hampering efforts to stop it.

“I am concerned that an underestimation of the oil spill’s flow may be impeding the ability to solve the leak and handle the management of the disaster,” he said in a statement Thursday. “If you don’t understand the scope of the problem, the capacity to find the answer is severely compromised.”

BP officials have said 5,000 barrels per day of crude, or 210,000 gallons, have been leaking for the past three weeks.

But a researcher at Purdue University has predicted that about 70,000 barrels of oil per day are gushing into the Gulf after analyzing videos of the spill.

Associate professor Steve Wereley said he arrived at that number after spending two hours Thursday analyzing video of a spill using a technique called particle image velocimetry. He said there is a 20 percent margin of error, which means between 56,000 and 84,000 barrels could be leaking daily.

“You can’t say with precision, but you can see there’s definitely more coming out of that pipe than people thought. It’s definitely not 5,000 barrels a day,” Wereley said.

He said he reached his estimate of 70,000 barrels per day by calculating how far and how fast oil particles were moving in the video.

Markey’s statement said that officials from BP, Transocean and Halliburton estimated a worst-case-scenario maximum flow at 60,000 barrels a day during congressional testimony May 4.

More than 260,000 barrels of oil spilled during the 1989 wreck of the supertanker Exxon Valdez in Alaska’s Prince William Sound.

BP spokesman Mark Proegler said that the company stands by its 5,000 barrels per day estimate. He said the company reached that number using data, satellite images and consultation with the Coast Guard and the National Oceanic and Atmospheric Administration. But there is no way to calculate a definite amount, he said.

“We are focused on stopping the leak and not measuring it,” he said.

Oil has been gushing into the gulf since April, when an explosion sank the Deepwater Horizon drill rig. The blast left 11 workers lost at sea.

BP said Thursday that it would attempt to insert a new section of pipe into the riser of its damaged undersea well to capture the leaking oil.

A previous effort to cap the gusher with a four-story containment dome failed when natural gas crystals collected inside the structure, plugging an outlet at the top.

BP, the Coast Guard, and state and local authorities have scrambled to keep the oil from reaching shore or the ecologically delicate coastal wetlands off Louisiana. They have burned off patches of the slick, deployed more than 280 miles of protective booms, skimmed as much as 4 million gallons of oily water off the surface of the Gulf and pumped more than 400,000 gallons of chemical dispersants onto the oil.

Investigators are still trying to determine what caused the April 20 explosion aboard the Deepwater Horizon.

BP has blamed drilling contractor Transocean Ltd., which owned the rig. Transocean says BP was responsible for the wellhead’s design and that oilfield services contractor Halliburton was responsible for cementing the well shut once drilled. And Halliburton says its workers were just following BP’s orders, but that Transocean was responsible for maintaining the rig’s blowout preventer.

– See videos of the oil spill at www.CNN.com