The U.S. Department of Transportation’s Federal Aviation Administration (FAA) proposes proposing a $52,000 civil penalty against Amazon, Inc., for allegedly violating the Hazardous Materials Regulations.

The FAA alleges that on June 2, 2014, Amazon offered UPS a non-specification cardboard box containing a flammable gas for air transportation from Whitestown, Ind., to Glendale, Calif.

The package held a 19-ounce container of Simple Air EZ Green HVAC Cleaner. Workers in UPS’s Louisville, Ky., sort facility discovered the container.

The FAA alleges the package was not properly marked, labeled or accompanied by shipping papers indicating the amount, type and hazardous nature of the material inside. The FAA also alleges Amazon did not provide required emergency response information with the shipment.

Amazon has 30 days from receipt of the FAA’s enforcement letter to respond to the agency.