(Reuters) – A cyber attack caused major printing and delivery disruptions on Saturday at the Los Angeles Times and other major U.S. newspapers, including ones owned by Tribune Publishing Co (TPCO.O) such as the Chicago Tribune and Baltimore Sun.

The cyber attack appeared to originate outside the United States, the Los Angeles Times reported, citing a source with knowledge of the situation.

The attack led to distribution delays in the Saturday edition of The Times, Tribune, Sun and other newspapers that share a production platform in Los Angeles, the Los Angeles Times reported.

Tribune Publishing, whose newspapers also include the New York Daily News and Orlando Sentinel, said it first detected the malware on Friday.

The West Coast editions of the Wall Street Journal and New York Times were hit as they are also printed on the shared production platform, the Los Angeles Times said.

Tribune Publishing spokeswoman Marisa Kollias said the virus hurt back-office systems used to publish and produce “newspapers across our properties.” 

“There is no evidence that customer credit card information or personally identifiable information has been compromised,” Kollias said in a statement

The Wall Street Journal and New York Times did not immediately respond to requests for comment.

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.

A spokeswoman for the Department of Homeland Security said it was studying the situation.

“We are aware of reports of a potential cyber incident affecting several news outlets, and are working with our government and industry partners to better understand the situation,” said DHS spokeswoman Katie Waldman in a statement.

Representatives of the Federal Bureau of Investigation were not immediately available for comment.