MANCHESTER — An office building in downtown Manchester was evacuated this morning when a construction worker cut into a 2-inch natural gas pipe, a city fire official said.

About 50 people were outside for about 40 minutes and returned about 9:20 a.m., as firefighters closed valves and measured gas levels inside the building. The building, 1100 Elm St., houses the Social Security Administration and financial service companies.

District Fire Chief Jim Michael said gas-air concentrations were kept low because the building was being vented as part of an asbestos-removal project. The worker was removing a boiler when he cut the line, Michael said.