Capitol Police investigate a nationwide wave of suspicious letters mailed to congressional and election offices. Chad Robertson - stock.adobe.com

The warning included a photo of one of the suspicious envelopes, postmarked  DSA  with a return address in New York City that the Democratic Socialists of America formerly listed on its membership forms.

The organization said it no longer occupies the address, which it stopped using in 2013.

Other California lawmakers, including Democratic Rep. Zoe Lofgren and Independent Rep. Kevin Kiley, also reported receiving suspicious mail, while Democratic US Sen. Alex Padilla said a suspicious package addressed to his office had been intercepted by the US Postal Service before it arrived.

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4 California Rep. Zoe Lofgren's office also reported receiving suspicious mail. AP

4 Democratic US Sen. Alex Padilla said a suspicious package addressed to his office had been intercepted by the US Postal Service before it arrived. AP

Across the country, other members of Congress reporting suspicious mail included Reps. Seth Moulton, Maxwell Frost, Darren Soto, Ritchie Torres and Bonnie Watson Coleman, along with Sens. Mike Rounds, Chris Murphy, Lisa Blunt Rochester, Chris Coons, Kirsten Gillibrand and Amy Klobuchar.

Separately, the Santa Cruz County Sheriff's Office responded to a report of potentially hazardous materials at the Santa Cruz County Government Building at 701 Ocean Street. The building was evacuated as a precaution, with no injuries reported.