WASHINGTON — Federal law enforcement officials secretly seized years’ worth of a New York Times reporter’s phone and e-mail records this year in an investigation of classified information leaks. It was the first known instance of the Justice Department going after a reporter’s data under President Trump.

The seizure — disclosed in a letter to the reporter, Ali Watkins — suggested that prosecutors will continue the aggressive tactics employed under Barack Obama.

Trump has complained bitterly about leaks and demanded that law enforcement officials seek criminal charges against government officials involved in illegal and sometimes embarrassing disclosures of national security secrets.

News media advocates consider the idea of mining a journalist’s records for sources to be an intrusion on First Amendment freedoms.

A prosecutor notified Watkins on Feb. 13 that the Justice Department had years of customer records and subscriber information from telecommunications companies, including Google and Verizon, for two e-mail accounts and a phone number of hers. Investigators did not obtain the content of the messages themselves.

The records covered years’ worth of Watkins’ communications before she joined the Times in late 2017.

Shortly before she began working at the Times, FBI agents approached Watkins seeking information about a previous three-year romantic relationship with James A. Wolfe, the Senate Intelligence Committee’s former director of security, saying they were investigating unauthorized leaks.

She did not answer their questions.

Wolfe was not a source of information for Watkins during their relationship, she said.