FBI agents have arrested six people in Minnesota and California in connection with a terrorism investigation, media in Minnesota reported on Monday.

Several of those arrested were members of Minneapolis' sizable Somali population, Minnesota Public Radio said in a report. There were no further details provided about the investigation or possible criminal charges.

An FBI spokesman in San Diego confirmed a news conference was planned for Monday in Minneapolis but would not confirm the six arrests.

In February, a Minnesota man was indicted on charges of conspiring to support Islamic State and lying to federal agents investigating recruitment by militant groups.

Dozens of people from the Minneapolis-St. Paul area, many of them Somali-American youths, have traveled or attempted to travel overseas to support militant groups such as Islamic State or al Shabaab since 2007, according to U.S. prosecutors.