Three men were sentenced to prison Tuesday for plotting to travel to Syria to join the Islamic State (ISIS) group, as a federal judge concluded the second day of sentencing in a case that shed a light on terror recruiting in the state.

During what has become a highly contentious presidential campaign, controversy continues to swirl around Hillary Clinton's private email server she used during her position as secretary of state.

For Clinton, the interview indicates that the Justice Department's year-long probe is drawing to a close only four weeks before she is set to be formally nominated as the Democrats' choice to succeed President Barack Obama.

FBI Director James Comey said Tuesday that the Islamic State (ISIS) group is currently the main threat facing the United States, both in its efforts to recruit fighters to join it in Syria and Iraq and to have others carry out violent attacks on American soil.

With a growing number of Americans being influenced by ISIS due to social media and other campaigns, terrorist threats on US soil are real and have become the FBI's top priority.

Basing their assessment on increased social media chatter, American security agencies are warning of the possibility of ISIS terror attacks in the US in the near future.