SANDISFIELD — The amount paid to Massachusetts State Police from a private pipeline company for overtime security details in Otis State Forest is approaching the $1 million mark.

Invoices obtained by The Eagle show that Kinder Morgan paid state police $184,900.86 for October overtime work at the four-mile Massachusetts stretch of the Connecticut Expansion Project, a $93 million, 13-mile natural gas spur recently completed by its subsidiary, Tennessee Gas Pipeline Co.

The October payments bring the total payment to $958,000 for details that began in late April at the controversial start of tree-cutting work in a state-owned and protected section of state forest.

The November invoices are not yet available, according to a state police official.

The details were part of a larger security strategy at a construction site in this remote forest — one that became the most recent East Coast target in a spreading nationwide anti-pipeline movement since Tennessee Gas' dropped its Northeast Energy Direct pipeline, and since the Standing Rock, N.D. entrenchment ended last winter.

The new transmission line was built in an existing corridor with two older lines. But that corridor had to be expanded by cutting a roughly 29-acre swath of forest.

It was partly this, combined with larger climate change concerns, that drew activists to the area. The rallies and protests since early May have resulted in nearly 100 arrests, for which a handful of activists had another set of hearings in Southern Berkshire District Court on Thursday.

But now it is Kinder Morgan's payments to state police that is firing up activists and has even legal experts perplexed about the commingling of a powerful private company with the most powerful public servants to protect a controversial investment.

A Northeastern University law professor previously told The Eagle that this particular alliance is troubling.

"It raises questions in the minds of citizens, that 'Is this my government that's acting, or is this a private entity that's acting?'" said Peter Enrich, who specializes in state and local government and intergovernmental relations.

State police spokesman David Procopio has said the mission is to simply keep people and property safe, and that the overtime details don't affect regular on-duty work shifts.

"We do not view events or missions in terms of a party's financial interests or political sensitivity," Procopio told The Eagle. "Regardless of and without attention to how events are characterized or debated by participants or the media."

But as the atmosphere at the pipeline build turned tense over the last few months, and police more aggressive, questions about the arrangement ballooned in size and complexity.

When a group of young water protectors came to the area as part of the post-Standing Rock mission to continue their activism, the tenor shifted after months of friendly relations between police and an older, seasoned group of activists.

Last month a young woman and a state trooper tangled and ended on the ground after state police say she pushed the trooper's arm. On another day, 55 troopers and two police dogs were on hand after one man was subdued with a stun gun when he ran during an arrest.

Kinder Morgan also hired private security guards in unmarked cars from the Boston firm Ed Davis LLC, whose presence appears to have dwindled since summer. Kinder Morgan spokesman David Conover declined to comment about the extent of private security at present.

Heather Bellow can be reached at 413-329-6871 or @BE_hbellow