The bureau has lost several informants who have infiltrated groups under investigation, an anonymous FBI agent was quoted as saying in a report on the impact of the shutdown.
“We have lost several sources who have worked for months, and years, to penetrate groups and target subjects. These assets cannot be replaced,” the joint terrorism task force coordinator said.
Agents who had been working on an investigation into the MS-13 criminal gang said they were only able to communicate with Spanish-speaking informants through a conference call with a translator.
“Since the shutdown, I have not had a Spanish speaker in the division,” one agent said. “We have several Spanish-speaking informants. We are only able to communicate using a three-way call with a linguist in another division.”
One official said the government shutdown had “eliminated any ability to operate”. They added: “It’s bad enough to work without pay, but we can only conduct administrative functions while doing it. The fear is our enemies know they can run freely.”
The FBI told The Independent it had no comment.
In a statement, the bureau distanced itself from the report, adding: “This report is a product of the FBIAA, a nonprofit professional association, and was not issued by the FBI.”
Several FBI officers said the government shutdown meant they risked losing vital informants.
“Not being able to pay Confidential Human Sources risks losing them and the information they provide FOREVER. It is not a switch that we can turn on and off,” one official said in the report.
Another agent said they fear losing further informants because they “cannot secure safe spaces to meet with our informants and we cannot pay them for their information”.
Hundreds of thousands of federal workers have gone without pay because of the government shutdown, which shows no signs of a swift conclusion.
Donald Trump has refused to sign any bill that would reopen the government unless it includes more than $5bn (£3.84bn) in funding for a wall across parts of the US-Mexico border.
Democrats consider a wall ineffective in combatting illegal immigration, and want the president to reopen federal agencies before they enter negotiations over border security.
The workers who are furloughed or working without pay are struggling to make ends meet as the shutdown, already the longest in US history, dragged on to its 33rd day on Wednesday.
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