Australian police say they’ve blocked 230 people suspected of joining terrorist groups from leaving the country since August. In an interview Wednesday, Border Protection Minister Peter Dutton said Australia’s anti-terrorism units have talked to 86,000 people across the country since the summer. Among those prevented from leaving were two Sydney-born brothers, ages 16 and 17, who were stopped this month while attempting to board a flight for Turkey without their parents’ knowledge. Less than a week later, another 17-year-old boy was picked up on the same suspicion of heading to battlefields in Iraq and Syria. Authorities estimate 90 Australian citizens have traveled to Iraq and Syria to join ISIS and 20 have been killed in clashes. Anyone Australian who travels to or remains in the ISIS strongholds of Mosul and Raqqa without a legitimate reason could face up to 10 years in prison.