WASHINGTON (MarketWatch) — An Exxon Mobil executive on Friday told a House committee that the firm had met all regulatory standards even as the company takes full responsibility for an oil spill that dumped an estimated 42,000 gallons of crude into Montana’s Yellowstone River this month.

ExxonMobil Pipeline President Gary Pruessing and others said at a hearing of the House Railroads, Pipelines and Hazardous Materials Subcommittee no one yet knows the cause of the July 1 spill that spread nearly 1,000 barrels of toxic chemicals at least 80 miles downstream to Laurel, Mont. — the third major oil spill in the U.S. in 15 months.

Cynthia Quarterman from the Pipeline and Hazardous Materials Safety Administration said the investigation is ongoing and determining the cause of the oil spill will take several months. Examining the pipeline itself will take several weeks because high water currently prevents crews from removing it. Cleanup along the shoreline is underway.

However, there was some confusion regarding when the river itself will be cleaned up. The Environmental Protection Agency — part of the team that will determine how to safety clean the river — is giving Exxon until Sept. 9.

This was news to Pruessing.

Exxon Mobil hasn’t released a cleanup date, he said, but he also didn’t know anything about EPA’s announcement: “I’m not aware of any dates that the EPA has said,” Pruessing said.

Exxon Mobil and the EPA will work together with Montana officials to determine the most effective way to clean the river, Pruessing said.

Tester, a Democrat, appeared before the House pipelines subcommittee to make a statement at the beginning of the hearing and said Exxon needs greater regulation. In this case, Exxon was tasked with regulating itself and now “we’re paying a price for it,” he said.

“Does that sound familiar?” Tester said. “Wall Street had no regulators either and it lead to the collapse of our nation’s economy.”

But Rep. Denny Rehberg, a Montana Republican, thanked Pruessing for his presence in Billings. Pruessing said he would stay in Montana until he got the job done.

Both Pruessing and Quarterman are set to testify Friday before a panel of the House Energy and Commerce Committee’s energy subcommittee, which will hear testimony on pipeline safety legislation. Sen. Jay Rockefeller, D-W.Va.,  is currently trying to pass a pipeline safety bill in the Senate.