(CNN) About 30 furloughed federal employees were accidentally paid in an apparent glitch before the funds were recovered, The Washington Post reported Friday.

Friday marks three weeks of the partial government shutdown, and the first missed paychecks for the over 800,000 government workers who have been either furloughed or are working without pay.

The Post, citing a senior Interior Department official, reported that nearly three dozen employees at the Chemical Safety and Hazard Investigation Board -- which assesses industrial chemical problems -- as well as two other Interior Department employees had received checks from their payroll manager, Interior Business Center, after one of the employees entered the wrong payroll code, the official told the Post.

"As best we're told, the coder for the board was a new person who did not understand how to do the coding properly," the official told the Post.

Once the center realized the error, the board sent the employees an urgent email instructing them not to spend the funds.

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