The U.S. government covertly moved to expel two officials from the Chinese embassy earlier this year, after they drove onto a military base, The New York Times reported, citing anonymous sources familiar with the matter.

The newspaper reported on Sunday that one of the two Chinese officials is believed to be an intelligence officer operating under diplomatic cover.

The Chinese officials breached security at a base in Virginia this fall, and only stopped driving after fire trucks were used to block their path, the Times said.

A law enforcement official familiar with the episode confirmed to Reuters that the account in The New York Times is accurate.

An FBI spokeswoman declined to comment. The State Department did not immediately respond to a request for comment about the incident.

The Chinese Foreign Ministry and Chinese Embassy in Washington could not be immediately reached for comment.

Though the exact reason for why the Chinese officials drove onto the base in Norfolk, Virginia was unknown, American officials believe it may have been to test security, one source told the newspaper.

When they finally stopped driving, the Chinese officials told the military guards they had gotten lost.

Weeks later, on Oct. 16, the State Department issued new rules on Chinese diplomats which require them to notify the department before they have any meetings with local or state officials, or with educational and research institutions.

The United States in recent years has stepped up efforts to combat concerns about suspected spying by the Chinese.

Investigators have been asking American universities to keep a closer watch on students and visiting Chinese scholars, and last year U.S. President Donald Trump signed a law prohibiting the U.S. government from buying telecom and surveillance equipment from Chinese companies Huawei Technologies Co Ltd and ZTE Corp.

The administration also slapped tariffs on a variety of Chinese goods, and the Justice Department has aggressively pursued prosecutions of suspected spies.