Updated

Four people have been indicted on charges stemming from a 1999 arson at Michigan State University and were working on behalf of a radical environmental group, federal authorities said Tuesday.

The government said the four named in an indictment were affiliated with the Earth Liberation Front, an underground organization that has been listed among the FBI's top domestic terrorism targets. Federal authorities announced the unsealing of the indictment Tuesday.

The defendants are Marie Jeanette Mason, 46, of Cincinnati; Frank Brian Ambrose, 33, of Detroit; Aren Bernard Burthwick, 27, of Detroit; and Stephanie Lynne Fultz, 27, of Detroit. They have not yet been arraigned on the charges. Mason remained in custody Tuesday afternoon but authorities said the others had been released on bond.

An attorney for Ambrose declined comment Tuesday. A message was left seeking comment from an attorney for Burthwick. As of Tuesday afternoon, lawyers for Mason and Fultz were not listed on a federal court Web page.

The Dec. 31, 1999 fire caused roughly $1 million in damage to the university's historic Agriculture Hall. Michigan State officials, along with federal authorities, have been working the case since.

"This was an act of domestic terrorism, plain and simple," said Charles R. Gross, a U.S. attorney from Grand Rapids. "There's no two ways about it. The use of violence and the destruction of property to make a political statement cannot be tolerated in a civilized society."

The four defendants also are charged in the Jan. 1, 2000 arson of commercial logging equipment near Mesick, Mich., in Wexford County.

Shortly after the Michigan State fire was set, the Earth Liberation Front notified media claiming responsibility for the incident. ELF said Michigan State was targeted because of genetic engineering research related to crops.

It was the second major Michigan State campus fire in less than a decade. A 1992 arson at a Michigan State mink research facility and campus research offices caused damage estimated at more than $2.5 million overall. A radical environmentalist, Rodney Coronado, served more than four years in federal prison for his role in that incident.

Agriculture Hall was built in 1909 and is considered a landmark on the Michigan State campus in East Lansing. No one was injured in the fire, one of a string of criminal acts nationwide targeting universities, fur farmers, loggers and others.

The 1999 fire at Michigan State damaged offices for a project aimed at enhancing the use of crop biotechnology in developing countries.

Michigan State President Lou Anna Simon said incidents such as the arson could have a cost beyond the property damage if they have a chilling effect on research.

"There is an enormous 'people' cost to this," Simon said.

The FBI and other law enforcement officials would not discuss details of what led to a break in the case more than eight years after the incident.

The Earth Liberation Front has been connected to several eco-terrorism cases in the U.S. Last week, for example, a federal jury found a woman guilty of two counts of arson for being the lookout in the 2001 burning of the University if Washington's Center for Urban Horticulture by ELF members.

In the Michigan State case, all four defendants are charged with conspiracy to commit arson. That is punishable by five to 20 years in prison. Mason and Ambrose are each charged with arson, the most severe counts of which are punishable by seven to 40 years.

All four face charges in connection with the damage to equipment in Wexford County.