BOSTON (AP) — State regulators have ordered a halt on non-emergency natural gas work by National Grid after a mistake during routine maintenance caused service to be shut off to hundreds of homes in a Massachusetts city.

The Department of Public Utilities said the moratorium, imposed following Monday's pressurization incident in Woburn, would remain in place pending a safety review. It also requires National Grid have an inspector on site for any work that could produce "abnormal pressurization."

More than 1,200 gas workers have been off the job since being locked out by the company in June. Unions representing the workers say the continuing lockout is jeopardizing safety.

Three communities served by a different utility were hit by natural gas fires and explosions last month, leaving one person dead and some 25 others hurt.