Explosion in Boston: several gas explosions burned more than 60 homes in Lawrence, North Andover and Andover

A series of gas explosions destroyed several communities in Massachusetts Thursday, burning many homes, forcing evacuations into three cities and leaving at least four people in the hospital.

In the space of one hour, the state police received between 60 and 100 cases of fire structures and gas explosions in the Merrimack area. Columbia Gas' s customers in Lawrence, North Andover and Andover have been ordered to leave their homes immediately and National Grid has promptly announced its intention to cut off any electricity needed to stop the spreading.

Massachusetts state police dispatched soldiers to secure the affected areas and help city residents fleeing their neighborhoods during rush hours in the evening. The motorway exits and exit have also been closed to facilitate evacuation.

Lawrence General Hospital treats four patients injured in the blasts, said Jill McDonald Halsey, chief of marketing and communications, Washington Post. "We are in emergency management activation mode and we are ready for everything that comes."

The cause of the explosions was not immediately explained.

The Columbia Gas company had announced Thursday that it would improve gas lines in neighborhoods throughout the state, including the area where the explosions took place. Later Thursday, the National Grid electricity company announced plans to cut off all electricity in the affected areas. Local public schools will also be closed on Friday.

Phil DeCologero, a resident of North Andover and chairman of his board of directors, said the city was overrun with fire trucks, buzzing helicopters and screaming sirens. He first noticed streams of black smoke on State Road 1144.

"More than a dozen homes in North Andover have caught fire," he said, including one in front of a multi-family home attached to a day care canter. "We are a city of 30,000 inhabitants, 27 square miles. Given the number of fires, no municipality of our size could absorb this type of disaster at the same time. "

Massachusetts state police dispatched soldiers to secure the affected areas and help city residents fleeing their neighborhoods during rush hours in the evening.

Fire departments in neighboring areas have also sent help. Highway exits on and off the highway were closed to facilitate evacuation and emergency evacuation centers were opened in the areas.

Massachusetts Governor Charlie Baker issued a statement urging residents to "consider instructions from local authorities regarding important public safety announcements, including evacuations and suspension of gas use."

Fire departments in neighboring areas have also sent help. Methuen's police chief, Joseph Solomon, who responded to Lawrence's help, said that there were so many fires "that you can not even see the sky," according to Western Massachusetts News.

Gas pipelines can explode for a number of reasons, said Glen Stevick, a PhD in mechanical engineering and a consultant at Berkeley Engineering and Research. Pipelines can be damaged during construction or they can be old, poorly maintained and have structural defects.

A pipe in good condition should be able to withstand twice as much force as it normally does. Still, Massachusetts state police announced that gas lines were depressurized by Columbia Gas after Thursday's explosions.

"Most pipes should withstand more than three times the pressure at which they work, but over time, there may be damage that weakens the pipes," Stevick said. "There may be reasons to increase the pressure, which usually means there are areas where the pipe could be corroded or very old. If you keep a good database of your pipelines and periodically conduct hydro tests, it's the safest way to carry fuel, but it takes some diligence. "