The state homeland security chief is downplaying concerns that the city’s steam pipe system could be a potential terrorist target, noting yesterday that the utility has fixed a major flaw in the system that regulators discovered during the 2003 citywide blackout.

Michael Balboni, the state’s deputy secretary for public safety, said that while the July 18 explosion called attention to the steam system as a possible target, New Yorkers should not be worried about an attack.

Vulnerabilities in the city’s aging web of pipes that carries steam to more than 1,000 Manhattan customers, including major hospitals, came to the forefront after an explosion in Midtown killed one and shut down a section of the city near Grand Central Terminal for five days.

A group of local officials yesterday said they would question the power company that maintains the pipes, Consolidated Edison, at an August 7 City Council hearing about the explosion.

“I think it raises a lot of questions about the vulnerability of the entire system,” Council Member Daniel Garodnick, who represents the area, said. “We need to make sure that the protocols for inspection are adequate and that they are not vulnerable to the routine and they are not vulnerable to the truly nefarious.”

A problem energy experts had noted was illustrated by a breakdown in the steam system during a citywide power outage in August 2003. Energy experts warned that if the outage had occurred in winter, the steam pipes could have burst, turning Manhattan into a “frozen New Orleans” below 96th Street.

“There would have been a major crisis,” a consultant with the Energy Resources Group, Leonard Shapiro, said.

Since then, the utility has addressed the problem, Mr. Balboni said yesterday. He also addressed the system as a potential terrorist target. “Obviously, when you have the ability to have this explosive nature, of course you have a vulnerability,” he said, adding that Con Edison has “a whole host of ways to deny access at different critical junctures.”

A New York City Police Department spokesman, Deputy Commissioner Paul Browne, echoed Mr. Balboni’s assessment. “There’s much easier and more obvious targets than trying to construct an attack on a buried steam delivery system,” he said.

Yesterday, the frozen zone surrounding the gaping hole left by the explosion was reduced to one block on East 41st Street between Park and Lexington avenues. To aid businesses affected by the explosion, Mayor Bloomberg and Governor Spitzer called on the Small Business Administration to declare the incident a federal disaster.