Organizers of the so-called "Straight Pride" parade planned in Boston later this summer say they were sent "suspicious packages" that turned out to be "glitter and vague ominous letters."

In a blog post on their website, the organizers from the group Super Happy Fun America called the incident "the action of domestic terrorists."

At least three of the parade's organizers say the suspicious packages were sent to their homes and that police were contacted Monday. Authorities responded but found that the packagers contained no explosives or dangerous substances, the group said.

"The intended message, however, is completely clear. The sender wants Super Happy Fun America to know: We know where you live, and your families are within our reach," the group wrote.

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USA TODAY has reached out to Massachusetts State Police and the FBI for comment.

In a statement to CNN, FBI spokeswoman Kristen Setera said the bureau was investigating but that it does not believe there is a threat to public safety.

The group sparked criticism nationwide when they announced plans to hold a "Straight Pride Parade" in Boston to celebrate "the diverse history, culture and contributions of the straight community," which they call a "oppressed majority."

Last week, Boston approved their event application to hold the parade Aug. 31, however their request to hoist a "Straight Pride flag" on the city's flagpoles was denied. Mayor Marty Walsh, a Democrat who has been critical of the event, reportedly will not attend the parade.

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The group blamed Antifa for sending the packages and said they are "further proof" of the oppression that straight people face.

President John Hugo, Vice President Mark Sahady and organizer Samson Racioppi said they received the packages.

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This article originally appeared on USA TODAY: Someone sent 'Straight Pride' parade organizers glitter. They called police for 'suspicious packages'