Over the course of two years, the authorities said, a group of 10 people conspired to set fires to abandoned buildings and wooded areas in a rural North Carolina county. But what was more unusual, officials said, is what the people had in common: They were volunteer firefighters.

The arrest of the 10 firefighters in Robeson County came Tuesday amid a yearlong investigation into more than a dozen fires that were deliberately set in the southern part of the county, Sheriff Kenneth Sealey said in a statement.

The people accused range in age from 17 to 42 and volunteered at the Orrum Township Fire Department and the Fairmont Rural Fire Department. Combined, the accused face about 90 arson-related charges. Among the 10 defendants are a former police officer and a Department of Corrections employee.

No one was hurt in any of the fires the 10 people are accused of starting, Major Anthony Thompson of the Robeson County Sheriff’s Department said in an interview on Wednesday.