After seven people allegedly trespassed at Quabbin Reservoir, which supplies much of Boston’s drinking water, State Police increased their scrutiny of the vast water supply.
So far, there is no evidence that the five men and two women found outside the reservoir just after midnight Tuesday were planning sabotage, but State Police have ordered troopers to patrol the water source more frequently, as well as all other state water supply facilities such as Spot Pond, Weston, and Wachusett reservoirs and the Deer Island treatment facility, said David Procopio, State Police spokesman.
The announcement of the new patrols came on the one-month anniversary of the terrorist bombings at the Boston Marathon and served as a reminder of the fear that still exists following the April attack.
Boston FBI spokesman Greg Comcowich said the agency is investigating the trespassing allegations, but emphasized that such an investigation is standard whenever there is an incident around critical infrastructure like a reservoir, an electrical grid, or liquid natural gas facility.
He declined to comment on whether the trespassing episode raised concerns of more possible terrorism in the state.
But the incident led officials at the Massachusetts Water Resources Authority to conduct tests of the reservoir to search for contamination. There was none, said Frederick A. Laskey, executive director of the MWRA.
“We did thorough testing yesterday for a zillion things,” he said. “All those results are in. All the tests passed.”
At about 12:30 a.m. Tuesday, a trooper stopped the men and women as they were walking away from one of the reservoir’s entrances toward two vehicles. They told the trooper they were recent college graduates from the University of Massachusetts and Smith College. The men said they were chemical engineers who went to see the reservoir because it fit their scholarly interests, Procopio said. The group told the troopers they were from Pakistan, Saudi Arabia, and Singapore.
The Quabbin Reservoir, one of the largest man-made public water supplies in the country, can hold up to 412 billion gallons of water.
It is nearly impossible to contaminate a reservoir as big as the Quabbin, not without drawing immediate attention from law enforcement, said Jeffrey Addicott, director of the Center for Terrorism Law at St. Mary’s University School of Law in San Antonio, Texas.
A terrorist would need “truckloads” of a chemical or biological agent to poison the drinking water, Addicott said.
“The biological agent has to be concentrated, and if you have a reservoir that size, it’s going to break up to a degree that wouldn’t cause significant damage to anybody,” he said.
Laskey said the MWRA has “state-of-the-art monitoring stations throughout our system” that could detect any tampering with the water supply.
The names of the seven people were not released because no charges have been filed against them.
Procopio said police usually release the nationalities of suspects who were born outside the United States.
Globe correspondent Jaclyn Reiss contributed to this report.