WOBURN, MASS. (WHDH) - National Grid crews have shut off gas to hundreds of properties in Woburn after a gas technician introduced “excess gas” into the system, officials said, and state officials have ordered the utility company to stop all work until safety practices can be reviewed.

A crew performing routine maintenance on a regulator station in the area of Wyman and Hart streets about 11:30 a.m. Monday “inadvertently introduced excess gas” into the system, according to a National grid spokesperson.

The issue was quickly recognized and the crew has since reduced the system to normal operating pressures.

“There is no apparent damage to the system, which feeds approximately 300 homes through three miles of pipe,” the spokesperson said. “In addition, pressure-control devices at each property function as an extra safety measure to limit the flow of gas to safe and normal levels. As a precaution, and to confirm that there is no damage to the system, gas has been shut off to these 300 properties.”

But Monday afternoon, officials with the Department of Public Utilities — which has authority over the state’s gas distribution system — ordered “a moratorium on all work, except for emergency and compliance work, across the company’s entire service territory pending the results of DPU’s review of National Grid’s safety practices.”

The state is also requiring that National Grid have an inspector on hand for all work involving pressurization. The department says it will hire an “Independent Evaluator” to review the state’s pipeline infrastructure.

Before the gas is turned back on, National Grid says technicians will be going door-to-door to turn off meters and assess the system.

Woburn city officials and a National Grid spokesperson addressed the issue at a 4 p.m. press conference at Wyman Elementary School.

Christine Milligan, a spokesperson for National Grid, said that last month’s incident in Merrimack Valley was “completely unrelated to National Grid” and Woburn residents are not in danger.

“We’ll do an investigation to find out exactly what happened,” Milligan said.

Gas re-lights are expected to occur late this evening and into tomorrow morning.

In the meantime, Woburn Fire Chief Stephen Adgate urged residents to contact the fire department if they smell gas in or around their homes.

“We’re confident from a fire department perspective that the process in place is going according to plan,” Adgate said. “We do recommend that if anyone does smell gas around their homes, that they don’t hesitate to call us so we can go out and make sure that everything is going to be safe.”

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