New York, New York - The assistant director of the FBI's New York Field office, James E. Dennehy, warned in a staff email that the bureau is in a "battle" with President Donald Trump's new administration.

In an internal email obtained by the New York Times, Dennehy called on staff to "dig in" and uphold the FBI's independence even as the Trump administration continues to target officials involved in prosecutions related to the president.

The response came after the Department of Justice on Friday ordered the FBI to provide a list of individuals who investigated the Capitol insurrection.

About 6,000 FBI employees are expected to be named in such a list, many of which would likely be purged from the agency.

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"Today, we find ourselves in the middle of a battle of our own, as good people are being walked out of the F.B.I. and others are being targeted because they did their jobs in accordance with the law and F.B.I. policy," Dennehy reportedly said in the email.

According to him, Trump's purge has caused "fear and angst" among FBI employees and has had a noticeable effect on the bureau's ability to carry out its responsibilities.

About 10% of the FBI's personnel fall under Dennehy's purview as assistant director of the bureau's New York field office.

Several high-ranking FBI officials have been removed from their posts since Trump was inaugurated on January 20, including Spencer Evans, the bureau's top agent in Las Vegas, who informed staff on Thursday that he had been dismissed.

"I was given no rationale for this decision, which, as you might imagine, has come as a shock," Evans said in an email seen by the New York Times.