A 39-year-old Boston resident is expected to be arraigned in municipal court on a charge of willful and malicious burning in connection with a Sunday morning ballot box fire, police said.

The fire, set in a ballot drop box outside the main branch of the Boston Public Library, prompted Secretary of State William Galvin, the state's elections overseer, to direct local officials to step up their security and monitoring of the drop boxes set up to receive early-voting ballots. Galvin also asked the FBI to investigate the incident.

Boston Police announced Monday that members of the fire investigation unit had identified Worldy Armand as a suspect. Shortly before 11 p.m. on Sunday, officers assigned to a drug control unit saw a man, Armand, who matched the fire suspect's description while they were patrolling the Copley Square area, according to the police department. Police said they determined he had an active warrant out of Ipswich District Court for receiving stolen property and took him into custody.

Of the 122 ballots that were removed from the box after the fire, 87 were still legible enough to be processed, according to Galvin's office, and the Boston Elections Department plans to mail new ballots to the other 35 voters.

A directive Galvin issued to local election officials Sunday encourages them to monitor early-voting drop boxes with video surveillance, close or relocate the boxes in the late evening to prevent overnight tampering, relocate boxes to entryways or lobbies of city or town halls, and increase the frequency of ballot collections, with a "clear chain of custody" for ballots retrieved from the boxes.

For drop boxes located in areas not otherwise under surveillance, the directive "strongly encourages" that a security detail "guard the drop box when it cannot be monitored by election officials or other municipal officers."

The Boston Police Department said officers were called to a scene outside the Boston Public Library on Boylston Street around 4 a.m. Sunday where firefighters were "tending to smoke coming from an early voting ballot box." Crews extinguished the fire by filling the drop box with water.

According to Galvin's office, the Boston Elections Department had last emptied the box at 2:29 p.m. Saturday, and 122 ballots were inside when it was emptied Sunday morning after the fire. Eighty-seven were legible enough to be processed. The city's election department asked that anyone who dropped their ballot off outside the library between 2:30 p.m. Saturday and 4 a.m. Sunday to call (617) 635-2211 to check the status of their ballot, which can also be done at www.trackmyballotma.com.

City election officials will mail new ballots to the 35 affected voters, Galvin said, and original ballots "will be hand-counted to the extent possible" for affected voters who do not submit new ballots.

Galvin reported the incident to U.S. Attorney Andrew Lelling's office and asked that the FBI investigate the apparent "deliberate attack," according to the secretary's office.

"What happened in the early hours of this morning to the ballot drop box in Copley Square is a disgrace to democracy, a disrespect to the voters fulfilling their civic duty, and a crime," Galvin and Boston Mayor Martin Walsh said in a joint statement, which also asked voters "not to be intimidated by this bad act, and remain committed to making their voices heard in this and every election."

Lelling and FBI special agent in charge Joseph Bonavolonta said in a joint statement that federal officials are investigating "the attempted ballot box arson," and that it would be a top priority of their offices over the next several weeks "to help maintain the integrity of the election process in Massachusetts by aggressively enforcing federal election laws."

"Voters in Massachusetts can feel confident in the success of the information sharing protocols that we have established with our local, state and federal election security partners in advance of the 2020 election," they said. "We remain fully committed to working with these partners to protect our communities as Americans exercise their right to vote. Help from the public is also vital to our effort. We encourage members of the public to remain vigilant and immediately report any suspicious, election-related activity to us."