Customers at most Hannaford Supermarkets are unable to use credit or debit cards to pay for their purchases because of a computer problem that began this morning.

Customers can still pay by cash or checks, said Hannaford spokesman Eric Blom.

“Most our stores are not able to process electronic payments — we expect the problem to be fixed this afternoon,” he said.

The computer glitch does not pose a security risk, Blom said, but rather is an operational problem. Blom said Hannaford has 181 stores, and all but “a handful” are impacted by the problem. He wouldn’t say whether the problem was the result of third-party equipment or Hannaford equipment.

“We wouldn’t want to get into details, but we certainly are working with a software vendor to address the problem,” he said.

Blom also wouldn’t disclose what percentage of Hannaford’s sales involve credit or debit cards. He said he was unsure if freestanding ATMs at the stores were impacted by the glitch.

In 2007 and 2008, Hannaford’s computer system was attacked and breached. Computer hackers stole credit and debit card numbers between Dec. 7, 2007, and March 10, 2008, from Hannaford shoppers. More than 4 million card numbers were exposed. About 1,800 fraudulent charges had been made by the time Hannaford announced the breach on March 17, 2008.

In 2010, the Maine Supreme Court ruled that victims of that breach couldn’t sue for damages if they didn’t suffer financial losses, physical harm or identity theft.