Tribune Publishing Co. newspapers across the country were also affected, including The Chicago Tribune, Baltimore Sun, Annapolis Capital-Gazette, Hartford Courant, New York Daily News, Orlando Sentinel and Fort Lauderdale Sun- Sentinel.
The attack came from a "foreign entity" aiming to "disable infrastructure, more specifically servers", rather than steal the data, the paper's source explained.
Most San Diego Union-Tribune subscribers were without a newspaper on Saturday as the virus infected the company's business systems and hobbled its ability to publish, the paper's editor and publisher Jeff Light wrote on its website. "We apologize to all of our readers for the inconvenience".
For Tribune subscribers, "there is no evidence that customer credit card information or personally identifiable information has been compromised", Kollias added. Teams from both companies were making progress against the virus, but weren't able to fix it before the newspapers went to print.
Tribune Publishing reported the attack to the Federal Bureau of Investigation on Friday, the Chicago Tribune said.
Delivery trucks are parked outside the Los Angeles Times Olympic Facility in Los Angeles Sunday Dec. 30 2018. A computer virus hit the newspaper
Tribune Publishing spokeswoman Marisa Kollias confirmed this in a statement, saying the virus hurt back-office systems used to publish and produce "newspapers across our properties".
On its Twitter account, Tribune Publishing Company acknowledged the issues, empathizing with customers affected.
In an update Saturday afternoon, the paper said that all publications within The Times' former parent company, Tribune Publishing, had problems with print production Saturday. "Thank you for your patience and support as we respond to this ongoing matter", The Times said in a statement.
The Southern California editions of the Wall Street Journal and The New York Times were affected as well, according to Light.
"The malware unfortunately impacted our timeliness and delivery of Saturday's Chicago Sun-Times", Kollias said. The papers had previously been part of Tronc, the previous name of Tribune Publishing.
A Tribune Publishing spokesperson didn't confirm the ransomware infection, but did say the incident was caused by "malware".
Blue light from power plant explosion causes confusion in New York City
Still, Deputy Inspector Osvaldo Nunez, the commanding officer of the 114th Precinct, conceded that the episode "was spectacular". The scattered power outage has also interrupted traffic at LaGuardia Airport, with only certain flights allowed to depart.