News organizations in particular seemed to take precautions on Wednesday. The device at CNN was found two days after a shooting at a Fox affiliate in Washington, which deepened the concerns over newsroom security that were raised when a gunman killed five people at a newspaper in Annapolis, Md., in June.

In San Diego, a building that houses The San Diego Union-Tribune newspaper, an office for Senator Kamala Harris, and other businesses was evacuated Wednesday morning after five boxes were spotted in a patio area.

The police closed the surrounding blocks and conducted an investigation, but the boxes only contained seemingly ordinary items: a football, a shoe, two children’s books and an empty bag of potato chips.

The boxes were not addressed, according to Kevin Wadhams, a lieutenant with the San Diego Police Department, and were left by an unknown person overnight.

Mr. Wadhams said that while officers were aware of the wave of pipe bombs being found, the police investigation was routine. But not everyone who worked in the building was so certain.

“It’s in context of all the other packages,” said Nathan Otto, 35, who works for the city auditor in San Diego, as he headed back to work after the evacuation. “Who knows how many false alarms are going around the country now?”

There were certainly others. The police were called to the Los Angeles Times building in El Segundo, Calif., after reports that suspicious envelopes were delivered there. The building was not evacuated, and officials said the packages did not contain explosive devices.