San Francisco Muni fare machines were back in working order Sunday after being shut down during a "cyber attack" on Friday and Saturday, transit officials said.
Officials with the San Francisco Municipal Transportation Agency were investigating what caused a malfunction with fare machines at underground stations Friday and Saturday, a Muni spokesman said Sunday.
The malfunction, which began sometime Friday, caused the fare machines at all the underground stations to display the message "You hacked," according to Muni spokesman Paul Rose. Rose said everything was operational on Monday, and he confirmed the malfunction was some sort of "cyber attack."
The incident resulted in passengers being unable to purchase transit tickets. Despite the malfunction, there was no impact to transit service, Rose said.
As of Sunday, all fare machines at the stations were back to normal, according to Rose, and the incident remains under investigation.
NBC Bay Area's Kris Sanchez contributed to this report.