"The FBI has confirmed a package was recovered last night in California, similar in appearance to the others, addressed to Tom Steyer," the agency tweeted on Friday.
The suspicious package was mailed to Steyer one week after the first similar pipe bomb package was intercepted at the same sorting facility on October 26.
Steyer, who is a billionaire hedge fund manager, is running two advocacy groups, "NextGen America" , an environmental non-profit committed to fights for a clean energy economy, and the political group "Need to Impeach", which focused on collecting signatures for the impeachment of President Donald Trump for being "unfit to be President".
The package sent to Steyer was the latest one of more than a dozen such devices mailed out across the US in recent weeks.
Federal law-enforcement authorities have arrested Cesar Soyoc who was suspected of a role in a series of mail bomb cases in Florida last week.
Those package bombs were sent to top Democrats and President Trump critics.
The 56-year-old Sayoc is currently held behind bars and waiting to be transferred to New York for trial.
(With inputs from agencies.)