The MTA said its OMNY system was back up and running this afternoon, after New York City transit commuters were unable to refill their physical OMNY cards Monday morning.

The MTA had posted on social media that the cards could not be refilled at vending machines, customer service centers or online. Several hours later, card refilling was fully restored, according to an MTA spokesperson.

From about 11:30 a.m., riders who use physical cards to ride subways and buses could not add more money to them if their accounts were low on funds.

The MTA had said people could still pay to ride using tap-to-pay on their phones, credit or debit cards, as well as preloaded OMNY cards.

The transit agency said the cause of the disruption remains under investigation.

The OMNY system, which stands for “One Metro New York,” fully replaced the yellow MetroCards at the start of this year. The OMNY system is largely digital, with people encouraged to use tap-to-pay methods. The vast majority of riders use their smartphones or credit cards to pay their fares, which are capped at $35 per seven-day period, provided they use the same device or card throughout.

Monday’s issues are the latest hiccup for the OMNY system, which was first rolled out in 2019. Last year, some customers complained of being billed multiple times for a single ride. The MTA previously spent about $4.5 million to fix an issue in which OMNY fare readers were falling off their mounts on buses.

MTA officials earlier this month said the agency would pilot a digital version of OMNY cards later this year.

This story has been updated with new information from the MTA.