SAN FRANCISCO (CBS/AP) — A computer glitch that inadvertently cancelled food stamp cards has left tens of thousands of Californians unable to use them to buy food.

Electronic Benefit Cards for nearly 40,000 people in 18 counties were rendered useless Monday because of computer problems that began Sunday.

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The state-issued cards contain money balances and can be used at supermarkets, farmers markets and some restaurants to purchase food and other items.

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Authorities say programmers updating software on the computer system accidentally canceled the cards.

Officials expected to have the problem fixed sometime Tuesday morning. Replacement cards also are available at county social service centers.

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