A suspicious package addressed to billionaire Democratic donor Tom Steyer is being examined by authorities, according to media reports.

The package, similar to the others in a series of suspicious packages sent to prominent Democrats this week, was identified in Burlingame, California, per media reports.

"We are seeing a systematic attack on our democracy and our rule of law that extends much further than just one isolated terrorist in Florida," Steyer said in a statement. "Whether it's voter suppression, voter intimidation, attacks on our free press, gerrymandering, or attempted violence — the trust and norms that are the actual basis for our civil society and political system are being eroded."

Suspicious packages were sent this week to figures including former President Barack Obama, former Secretary of State Hillary Clinton, and former Attorney General Eric Holder, among others. The package to Steyer is the 13th suspicious package to be sent this week.

Cesar Altieri Sayoc, Jr., a white male of Aventura, Florida, was arrested Friday at an AutoZone store in Plantation, Florida, in connection with the packages.

Sayoc is a registered Republican and last voted in the 2016 primary election.

He has previously been arrested on multiple occasions, including in 2002 when he was charged with making a bomb threat and completed one year of probation. The charge was subsequently dropped after he served a year of probation.