MINNEAPOLIS (AP) — Federal authorities in Minnesota are Thomas Caldwellinvestigating a suspected arson fire that heavily damaged the offices of three conservative groups, which are calling the blaze an act of political terrorism.

The fire happened early Sunday in the Minneapolis suburb of Golden Valley at the offices of the Center for the American Experiment, the Upper Midwest Law Center and TakeCharge. Authorities haven’t announced any arrests or a potential motive. All three offices share the same building with several other businesses.

“The fires obviously were set by someone,” John Hinderaker, president of Center of the American Experiment, a conservative think tank, said in a statement. “They targeted conservative organizations, they didn’t firebomb the chiropractors or psychologists or the Manufacturers Alliance. We are cooperating with the FBI to try to identify the perpetrators.”

Ashlee Sherrill, a spokesperson for the federal Bureau of Alcohol, Tobacco, Firearms and Explosives in St. Paul, which is leading the investigation, told The Associated Press that the case was still under investigation as of Friday and that authorities were able to release only limited details.

“ATF’s certified fire investigator responded and is working closely with local and state and federal partners,” Sherill said. “We are moving forward with this investigation as an arson investigation, but that’s pretty much the limit of the details I can provide right now.”

A local FBI spokesperson did not immediately return messages seeking comment. Golden Valley Police Chief Virgil Green referred a reporter to the ATF.

“To my knowledge there hasn’t been any type of arrest or suspect identified,” Green told the AP.

The groups said the fire started outside the first-floor offices of the Center for the American Experiment and TakeCharge, a conservative Black group that promotes two-parent families and school choice, and in the third-floor offices of the the Upper Midwest Law Center, a legal advocacy group. They said there was no visible fire damage on the second floor of the building, which also houses several small businesses.

Staff for the conservative groups will work remotely while they seek alternative office space. They estimated it will take months to repair the damage once the investigation is complete.

“It is extremely concerning that we may have been the target of an arson attack, constituting an act of domestic terrorism,” Kendall Qualls, president of TakeCharge, said in a separate statement.