3:35 p.m. Update: Amtrak spokeswoman Christina Leeds says the issue was resolved as of 3:20 p.m.

Original post: Amtrak’s Quick Trak ticket self-service kiosks across the country are experiencing software problems, according to Christina Leeds, a spokeswoman for the railroad.

The Maryland Transit Administration issued an alert for passengers on its Maryland Area Regional Commuter trains. Tickets may be purchased on board trains, using cash only, the MTA said. The state pays Amtrak $47 million to operate the Penn Line on tracks that Amtrak owns.

Amtrak is working on the problem, Leeds said, but a cause has yet to be diagnosed. The outage begain between 2:45 and 2:50 p.m., she said. The problems are not affecting machines used by ticket agents.