A National Grid USA technician accidentally released "excess gas" into part of its gas system during routine maintenance in a city north of Boston, the gas and electric utility disclosed Oct. 8, prompting Massachusetts regulators to halt all nonessential work across the company's service territory.

The crew spotted the error quickly and reduced the system to normal operating pressures within minutes, National Grid tweeted. The company said it does not believe that the mistake damaged the system, which serves about 300 homes in Woburn, Mass., along three miles of pipe. The utility shut off gas service in the affected area as a precaution but said each property has a pressure-control device installed.

"The area, which surrounds a regulator station at Wyman [and] Hart streets in Woburn, is safe and National Grid has the situation under control," National Grid tweeted. "We will be turning off meters in the immediate area and assessing the system before starting the relight process." National Grid said it expects to fully restore service within the week.

Following the incident, the Massachusetts Department of Public Utilities ordered National Grid to stop all system work that is not an emergency or compliance-related until the department reviews the company's safety practices, the Boston Herald reported Oct. 9.

The state also told National Grid to have an inspector on-site for any work that could lead to abnormal pressurization until the statewide assessment is done, said Peter Lorenz, a spokesman for the state's Executive Office of Energy and Environmental Affairs, according to the Herald.

The state regulator in late September launched a statewide review of natural gas distribution systems, including National Grid's, after a deadly series of explosions and fires along NiSource Inc. infrastructure in the communities of Lawrence, Andover and North Andover, which are just north of Woburn. The department will hire an independent evaluator to do the assessment, which is expected to encompass the physical integrity and safety of gas distribution systems in the state as well as utilities' operation and maintenance policies, safety protocols and other practices.