ST. PAUL — Six people were arrested Sunday in connection with a terrorism investigation in Minnesota, where authorities have been tracking youths who have traveled or tried to travel to Syria to fight with militants, including the Islamic State group, authorities said.

A spokesman for the Minnesota U.S. Attorney’s Office said the arrests were made in Minneapolis and San Diego but there is no threat to public safety. Spokesman Ben Petok did not give details about the charges. He said more information would be released Monday.

The U.S. Attorney’s Office and the FBI planned a news conference Monday to announce details. The news conference was billed in a press release as an announcement of a joint terrorism task force operation.

Kyle Loven, spokesman for the Minneapolis office of the FBI, said six people were arrested Sunday but gave no further details. An FBI spokesman in San Diego referred questions to Loven.

Authorities say a handful of Minnesota residents have traveled to Syria to fight with militants within the last year. At least one Minnesotan has died while fighting for the Islamic State.

Since 2007, more than 22 young Somali men have also traveled from Minnesota to Somalia to join the militant group al-Shabab.

Four Minnesotans have already been charged in connection with supporting terror groups in Syria, including the Islamic State group.