Suspicious letters were sent to the main organizers of the Boston Straight Pride Parade Monday, one of the organizers told NBC10 Boston, bringing out specialists to investigate.

Bomb squads responded to locations in Woburn, Salisbury and Malden, but the FBI has said there was no danger to the public. A source said there was glitter and verses from the Bible in the letters.

After investigating, police said the letters appeared to be a legal use of the mail and that no laws were broken.

The letters did not have a return address and were taped shut, organizer Samson Racioppi said.

Tuesday, the group said one of its ambassadors, a Malden man, received a letter in the mail. It was not opened before the FBI took possession of it.

"I could hear something shaking ... it was probably bigger than grains of sand and I was immediately suspicious," Racioppi said.

The Boston Pride Parade is set for Saturday, but a different group is facing harsh criticism for its planned “Straight Pride Parade.”

The controversial parade is scheduled for Aug. 31.

The packages contained glitter and Bible verses and were signed at the bottom "Happy Pride" in rainbow colors, a source with ties to the investigation said.

One verse was Psalms 86:15: "But you, Lord, are a compassionate and gracious God, slow to anger, abounding in love and faithfulness..."

The FBI confirmed that there is no threat to public safety. It is working with local agencies to identify the source of the threats.

Authorities haven't yet said if the incidents are related.

The letters do not appear to have broken state or federal laws, according to a law enforcement source at the scene in Malden.

"Right now we believe this is a legit use of the mail," the source said.

The scene was already cleared about two hours after the initial report in Salisbury, near the New Hampshire border, police said there. No one was hurt, and officers said they cleared the area and requested assistance after the person reported the letter "out of an abundance of caution."

The letter sent to Salisbury was processed in Columbus, Ohio.

NBC Boston

In Woburn, the fire department confirmed that responded to a suspicious package in the back of the main parking lot in Woburn Center.

The letters won't stop the parade from going forward, Racioppi said. "If anything, it will make us more determined."

The parade is meant to be a celebration of the straight sexual orientation, according to the president of the Super Happy Fun America group behind the parade, John Hugo.

"We're a sexual orientation just like many others," he said last week. "We don't hate anyone. We just want to have our own celebration just like everybody else has a right to. All people from all communities are welcome, so long as they show mutual respect."

A growing chorus of voices is calling for the vice mayor of Dixon, California to step down after his column proclaiming July as "Straight Pride American Month." KCRA's Mike Luery reports.

Hugo said the parade would go from Copley Square to Boston City Hall, with former Breitbart editor Milo Yiannopoulos, a right-wing personality who's been banned from several social media platforms, serving as grand marshal.

While its organizers say they are serious about bringing the parade to Boston, the parade has been widely mocked as a stunt — it was announced at the start of LGBTQ pride month, and its many vocal opponents have argued that straight people haven't suffered the same years of oppression that prompted the widespread LGBTQ pride celebrations.

Mayor Marty Walsh has said that the city can't stop the parade, though he won't attend it.

Sophie Reardon, Perry Russom, Ally Donnelly, Eli Rosenberg and Asher Klein contributed to this report.