She said she knows of two clients who are working from home, but most can't. The issue, she said, is not access to the buildings but no access to infrastructure services to run their businesses, primarily phone service.

Eileen Frank, president of J.P. West, a brokerage in New York City, concurred. “This will be a significant [business interruption] loss.”

She said many clients were just getting back into their buildings between today and tomorrow, but some, such as restaurants, had no customers coming through the doors–a basis for loss of income claims under their policies.

The New York City Office of Emergency Management said that large sections around the site, covering 42nd to 45th Streets around Third Avenue, that were closed down have reopened. People have access to most of the buildings and there remains a 100-foot area around the explosion that is still cordoned off.

OEM said on its Web site today that three buildings remain closed. Eight buildings have reopened, but access does not include retail spaces and courtyards.

A spokesman for Con Edison, the utility that operates and maintains the steam pipes throughout the city, said the company has insurance to cover property damage but it does not cover business interruption. Con Ed and the Grand Central Partnership are offering businesses in the area no-interest loans up to $10,000.

Ms. Emek explained that while business interruption policies traditionally cover closures from civil orders, the policies have endorsements covering loss of income, which many area businesses are suffering.

Besides business interruption and some property damage concerns, there is the possibility of environmental claims since some asbestos debris was found, but environmental officials said there was no airborne asbestos. Asbestos was used to insulate the pipe that was laid down in the 1920s.

Ms. Frank said there probably would be environmental claims as people clean up and possibly discover asbestos-laced debris in their buildings and offices. There is also the possibility some persons may suffer delayed illness as a result of being covered with debris. Con Ed said it had requested that anyone whose clothing was covered with debris from the incident turn it in so the utility can safely dispose of it.

Earlier this week the Associated Press reported that Travelers Indemnity Companies and Allianz Global Risk U.S. filed petitions in New York State Court to monitor the cleanup and ensure evidence is saved from the blast.

Yesterday, the city and Con Ed granted the insurers access to the cleanup, a Con Ed spokesman said.

A request for comment and copies of the filings from the insurers was not immediately returned.