Washington (CNN) The FBI has lost several informants that had penetrated groups at the center of terrorism investigations.

A task force targeting interstate meth and heroin traffickers has run out of funds to pay for controlled purchases.

Agents working a multi-year MS-13 investigation have resorted to conference calls to communicate with Spanish-speaking sources.

As the partial government shutdown entered a second month, dozens of anonymous FBI officials took the rare step to share how the lack of funding has kneecapped operations in a report released Tuesday by an agents advocacy group.

The accounts -- compiled by the FBI Agents Association, which represents most of the bureau's active duty special agents -- mark a new front in the damage caused by the country's longest shutdown: weakened national security.

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