When more than 300 protesters assembled in May at the Holiday Inn in Lakewood, Colorado — the venue chosen by the Bureau of Land Management (BLM) for an auction of oil and gas leases on public lands — several of the demonstrators were in fact undercover agents sent by law enforcement to keep tabs on the demonstration, according to emails obtained by The Intercept.

The “Keep it in the Ground” movement, a broad effort to block the development of drilling projects, has rapidly gained traction over the last year, raising pressure on the Obama administration to curtail hydraulic fracturing, known as fracking, and coal mining on federal public lands. In response, government agencies and industry groups have sharply criticized the activists in public, while quietly moving to track their activities.

The emails, which were obtained through an open records act request, show that the Lakewood Police Department collected details about the protest from undercover officers as the event was being planned. During the auction, both local law enforcement and federal agents went undercover among the protesters.

The emails further show that police monitored Keep it in the Ground participating groups such as 350.org, Break Free Movement, Rainforest Action Network, and WildEarth Guardians, while relying upon intelligence gathered by Anadarko, one of the largest oil and gas producers in the region.

“Gentlemen, Here is some additional intelligence on the group you may be dealing with today,” wrote Kevin Paletta, Lakewood’s then-chief of police, on May 12, the day of the protest. The Anadarko report, forwarded to Paletta by Joni Inman, a public relations consultant, warned of activist trainings conducted by “the very active off-shoot of 350.org” that had “the goal of encouraging ‘direct action’ such as blocking, vandalism, and trespass.”

The protesters waved signs and marched outside of the Holiday Inn. The auction went on as planned and there were no arrests.

“I believe the BLM reached out to us,” Steve Davis, the public information officer for the Lakewood police, told The Intercept about preparations for the protest. He added that the protest was “very peaceful.”

“Our goal is to provide for public safety and the safety of our employees,” says Steven Hall, the BLM Colorado Communications Director, when asked about the agency’s undercover work. “Any actions that we take are designed to achieved those goals. We do not discuss the details of our law enforcement activities.”

BLM reimbursed the Lakewood police for costs associated with covering the protest, the emails and a scanned copy of the check show.