Don't put those masks away just yet.

The U.S. Justice Department said it's appealing the ruling by a federal judge that voided the mask mandate for public transportation.

DOJ spokesperson Anthony Coley said a notice of appeal had been filed in light of the determination by Centers for Disease Control and Prevention that wearing a mask "remains necessary to protect the public health."

The CDC said it had asked the DOJ to appeal. The public health agency continues to recommend that people wear masks in all indoor public transportation settings and says "wearing masks is most beneficial in crowded or poorly ventilated locations, such as the transportation corridor."

The Biden administration had previously insinuated that it might appeal the ruling by U.S. District Judge Kathryn Kimball Mizelle after checking with the CDC.

The department's decision to appeal comes just two days after Mizelle ruled that the CDC had exceeded its authority and had failed to follow proper rule-making procedures.

After the judge's ruling on Monday, many airlines ditched their requirements for passengers to wear masks while traveling.

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