COLUMBUS, Ohio — A major voting machine maker has cautioned its customers in 34 states to look out for a programming error that may cause votes to be dropped.

At least 1,000 total votes were dropped in nine Ohio counties over the course of a handful elections back to 2006, including the March presidential primary, though the error was in all cases discovered and corrected within several hours. Premier Election Solutions Inc. previously had said complications with antivirus software caused the problem, but on Tuesday the company said in a product advisory that the problem is with the machines themselves.

The error occurs when multiple memory cards are being uploaded at the same time, and it is more likely to occur in jurisdictions that have several voters and use touch-screen voting systems, said Premier spokesman Chris Riggall.

Allen, Texas-based Premier, a unit of North Canton-based Diebold Inc., supplies touch-screen voting systems as well as scanners for paper ballots. The problem is more likely to occur in touch-screen systems because they use more memory cards, one for every touch screen.

Premier said in its product advisory that the problem can be corrected as long as officials monitor whether the memory cards are being uploaded, and if they are not, reload them until they are.

“We are communicating to customers around the country, making sure that we’re answering any questions concerning it,” Riggall said.

In Ohio, the dropped votes were discovered within several hours by election officials who noticed the memory cards weren’t being read properly. Workers re-fed the cards into the server until they worked, and the votes were added to the overall vote totals.

After Premier blamed the problem solely on antivirus software, officials in Ohio’s Butler County kept testing the machines and claimed that there was a problem with the machines themselves. That was later verified by Premier’s own testing. The company said the software can cause the error, but that the programming glitch can produce the error even when the software isn’t used.

Ohio will continue to use the Premier machines in the Nov. 4 election. Secretary of State Jennifer Brunner said identifying the cause of the problem will enable the state to prepare election officials to watch for the problem and correct it should it resurface.

“We are finalizing plans that will walk board officials through the process of identifying the problem, loading the affected memory cards and verifying that the votes are counted,” said Brunner spokesman Kevin Kidder.

The company and state election officials said there are multiple layers of security in place, such as post-election audits that match voting machine totals with a paper trail, that will ensure that no votes are missed.

Cuyahoga County, Ohio’s largest county and the home of Cleveland, dropped Premier touch-screen systems in 2007 after the system malfunctioned. The company sued the county for breach of contract. Brunner then countersued, citing the dropped votes that the company acknowledged in its letter to Brunner this week.

Premier spokesman Riggall said he could not comment on the lawsuit.