City Council members peppered with tough questions a Consolidated Edison vice president, William Longhi, yesterday at a hearing on the Midtown steam pipe explosion that killed one and injured dozens.

Although Mr. Longhi testified at length about Con Edison’s response to the July explosion, he offered no explanation of what caused the pipe to rupture, an omission that rankled council members.

“What do you think happened?” Speaker Christine Quinn asked him repeatedly.

“You may not have all the answers and all the Ts crossed and all the Is dotted. I can accept that,” Ms. Quinn said. “But I cannot accept that you have absolutely nothing to tell us about why this may have happened.

Mr. Longhi said the cause of the rupture would be determined by an investigation that could take three months. “We really do not want to speculate on this,” he said. Council Member Peter Vallone, a Democrat of Queens, predicted that Con Ed’s investigation would be a “complete whitewash.”

“I’m just about as sick of sitting here asking questions as I’m sure Con Ed must be of coming up with ways to evade them,” Mr. Vallone said. “Con Ed sounds like a criminal who’s lawyered up.”

Council members objected to yesterday’s absence of Con Edison’s CEO, Kevin Burke. Council Member Leroy Comrie, chairman of the Committee on Consumer Affairs, which held the hearing, called his failure to show up “a slap in the face to this city.”

Mr. Longhi said Mr. Burke was at work, and that they had both agreed that Mr. Longhi would be the best person to testify.

Asked whether New Yorkers should have confidence in Con Edison, Mr. Longhi said, “We’ve established ourselves year after year as the most reliable utility in the United States.”

Mayor Bloomberg defended Con Edison, saying he was satisfied with the pace of reconstruction. “I think Con Ed has a good sense of who’s an expert on what went on at the site,” he said of the decision to send Mr. Longhi.