Chinese hackers targeted data from phones used by Donald Trump and JD Vance, and members of Kamala Harris’ campaign.

People close to the matter told the New York Times that the hackers are believed to have breached American telecommunications networks, and that investigators are still trying to determine what information, if any, they gleaned.

But FBI and national security officials are deeply concerned about the possible extent of the compromised data and the range of people who may have been targeted, according to the Times report.

Investigators refer to the hacking campaign as “Salt Typhoon.”

Intelligence about who a presidential candidate and his running mate talked to or exchanged texts with could prove highly valuable to China, a U.S. adversary eager to influence the upcoming election on the local, state, and federal level.

The Trump-Vance campaign was made aware this week that the two men were among the hacking effort’s targets, who also included a number of other people, inside of government and out-, officials told the Times.

In addition to the Republican presidential ticket, the targets also included prominent Democrats, including people affiliated with the Harris campaign, the Wall Street Journal reported.

The Journal also said that one of its own reporters who was involved in covering the breaches last month had been targeted.

According to the Journal’s report, the telecom firms breached in the attack include Verizon, AT&T, and Lumen.

“We are aware that a highly sophisticated nation-state actor has reportedly targeted several U.S. telecommunications providers to gather intelligence,” Verizon spokesman Rich Young told the Journal. He also said that the company is working with law enforcement to understand the scope of the breach.

The attack comes less than two weeks out from an election in which Trump and Harris are currently polling in a dead heat. Any outside influence could threaten to tip the deadlocked race one way or the other.

Earlier in the race, Trump’s team was targeted by hackers from Iran. As part of a spear-phishing campaign that used fake emails posing as a number of public figures—including Ginni Thomas, the wife of Supreme Court Justice Clarence Thomas—to target Trump campaign officials.

Those hackers were able to get away with some information related to Trump’s debate prep and possible vice-presidential candidates, according to an indictment filed against the three Iranian men. It also said that they leaked some of the stolen information to the media in an effort to sow discord around the election.