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, a Premier spokesman, Chris Riggall, said.

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.