CHICAGO (CBS/AP) – A group of Chicago anti-war activists has refused to testify before a grand jury, calling the federal subpoenas a “fishing expedition.”

Maureen Murphy and eight other activists skipped a grand jury hearing at the Dirksen Federal Building Tuesday morning, defying federal subpoenas.

Murphy said the subpoenas are part of a “fishing expedition” by federal authorities seeking to silence the anti-war movement.

Federal investigators have subpoenaed more than 20 anti-war activists around the country since September, when the FBI raided the homes of several organizers in Chicago and Minneapolis.

Federal officials have said they can’t comment on grand jury matters.

But when the FBI conducted the raids last fall, officials said they were seeking “evidence relating to activities concerning the material support of terrorism.”

The warrants from the raids suggested the FBI was looking for connections between anti-war activists and militant groups in Colombia and the Middle East.

None of the activists has been charged with a crime.