According to The Daily Mail, the FBI has admitted to gathering secret intelligence about the Burning Man festival since 2010.

In a heavily-redacted document in response to a request under the Freedom of Information Act, the service said its Special Events Management unit has kept files on festival-goers to “aid in the prevention of terrorist activities and intelligence collection.” The FBI also said its involvement in the Black Rock Desert gathering was “even more critical in the light of the ongoing war on terrorism and the potential for additional acts of terrorism being committed in the United States.” They also noted, “The greatest known threat in this event is crowd control issues and use of illegal drugs by participants.”

The 29th annual Burning Man is taking place this week in the Black Rock Desert of Nevada.