The FBI arrested Claremont resident Martin Calvin Yarbrough Jr, 48, on Jan. 28. Yarbrough allegedly mailed threatening letters containing white powder to offices of the Los Angeles County Department of Children and Family Services and the Edmund D. Edelman Children’s Court.

Federal prosecutors said Yarbrough sent 13 letters between November 2008 and May 2010. On the day of his arrest, Yarbrough entered a not guilty plea to 13 counts of making threats and hoaxes. He was released later that day on a $25,000 bail.

According to a press release from the Los Angeles County Sheriff’s Department, the envelopes Yarbrough allegedly sent contained one of either a “white powdery substance”—later determined to be boric acid—or a “bluish granular substance,”—which was found to be warfarin, a chemical commonly used as a rat poison.

The buildings were evacuated upon the discovery of the envelopes, though no one became sick during the incidents.

“Typically when something like this happens, the first people who are called are the local police departments,” said Assistant United States Attorney Sherilyn Peace Garnett.

After the evacuation, hazardous materials teams came to the sites to test the material in the envelopes. The FBI’s Weapons of Mass Destruction Coordinator also responded to the threat.

The Los Angeles County Public Health Laboratory tested the contents of the envelopes for biological hazards, and found none.

A representative of the Claremont Police Department said that Yarbrough is “a former employee of the City of Claremont,” but declined to comment further on Yarbrough’s employment.

According to the DCFS website, its duties, in part, consist of educating parents about how to care for their children, preventing and halting child abuse, and finding adoptive homes for children in foster care. The Edmund D. Edelman Children’s Court, according to the Children’s Law Center of Los Angeles, is “the country’s first courthouse especially designed for children and families.”

At the time of the press release, made on the same day as Yarbrough’s arrest, authorities declined to speculate on the man’s possible motive.

According to Thom Mrozek, U.S. Attorney Spokesman, Yarbrough’s trial has been set for March 22. His trial will take place in a federal court in Los Angeles, Garnett said.

If the court finds Yarbrough guilty on all charges, he would face a maximum of five years in federal prison for each count of making threats and hoaxes for a total of 65 years of incarceration.