The Federal Aviation Administration on Saturday ordered MD-11 and MD-11F aircrafts to be grounded as authorities investigate the deadly UPS plane crash in Kentucky.

The emergency airworthiness directive came after UPS and FedEx said they are voluntarily grounding their fleets of McDonnell Douglas MD-11 cargo planes "out of an abundance of caution" following a deadly crash at the UPS global aviation hub in Louisville.

The FAA's order was issued "because the agency has determined the unsafe condition is likely to exist or develop in other products of the same type design," the document obtained by CBS News read.

"We are assessing any potential safety issues and will ensure appropriate corrective actions are taken," the agency said in a statement.

The crash on Tuesday at UPS World

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