By Siobhan Hughes Of DOW JONES NEWSWIRES WASHINGTON (Dow Jones)--BP PLC (BP, BP.LN) Chief Executive Tony Hayward on Thursday insisted he was "not involved" in key decisions about a mile-deep oil well that exploded two months ago, frustrating U.S. lawmakers hoping to gain more details about the disaster. "I wasn't involved in any of that decision-making," Hayward told House Energy and Commerce Committee Chairman Henry Waxman (D, Calif.) Hayward also said federal regulators had signed off on BP's well design, offering a preview of the company's defense. BP is facing multiple probes, including Justice Department civil and criminal investigations. Congressional investigators have unearthed evidence they say shows that BP ignored warnings from contractors and BP personnel in order to save money. Three days after receiving a letter detailing the congressional findings, Hayward told the committee that he was "not prepared to draw conclusions." Among other things, the House panel has found that BP opted for the cheaper of two options in an important well-design decision, using a single string of steel casing from the sea floor to the bottom of the well. BP could have used a "tieback" method that would have provided twice as much protection, according to evidence released by the House Energy and Commerce Committee. "BP used a more dangerous well design to save $7 million," Waxman said, citing documents obtained by the committee. Replied Hayward: "I believe that document also highlights that the long-term integrity of the well would be best served by a long string." He said that "a long string is not an unusual well design in the Gulf of Mexico." Waxman became visibly frustrated with Hayward. "Are you failing to cooperate with other investigators as well? Because they're going to have a hard time reaching conclusions if you stonewall them, which is what we seem to be getting today," Waxman said. "I'm not stonewalling," Hayward said. "I simply was not involved in the decision-making process." -By Siobhan Hughes, Dow Jones Newswires; (202) 862-6654; siobhan.hughes@dowjones.com (END) Dow Jones Newswires June 17, 2010 13:36 ET (17:36 GMT)