A computer network used by Democratic presidential nominee Hillary Clinton’s campaign has been compromised, according to Reuters .

The hack is the third in a series targeting the Democratic establishment. The Democratic National Committee and the Democratic Congressional Campaign Committee were also targeted, reports earlier this week said.

The Clinton campaign had no immediate comment, according to the report. Reuters first learned of the intrusion Friday.

The U.S. Department of Justice national security division is looking into whether or not the series of hacks threatens U.S. security, Reuters said.

According to CNN, the FBI is investigating a possible hack of the Clinton campaign’s computers and email system.