National Grid held a news conference in Woburn on Tuesday after a worker created a potentially dangerous situation in the town on Monday night.

The worker unintentionally allowed gas lines to overpressurize. The recent gas explosions in Merrimack Valley were reportedly caused by overpressurized Columbia Gas lines.

The Department of Public Utilities told National Grid to discontinue new gas installations, except in emergency cases, until there's a full review of the incident.

Bruce Gellerman, WBUR reporter. He tweets @AudioBruce.

Robert Forrant, professor of history at UMass Lowell