Trash bags stuffed full of used medical gloves, some visibly soiled, some even blood-stained, litter the floor of a warehouse on the outskirts of Bangkok.

Nearby is a plastic bowl, filled with blue dye and a few gloves. Thai officials say migrant laborers had been trying to make the gloves look new again, when Thai health authorities raided the facility in December.

There are many more warehouses just like it still in operation today in Thailand -- trying to cash in on the demand for medical-grade nitrile gloves, which exploded with the coronavirus pandemic. And they're boxing up millions of these sub-standard gloves for export to the United States, and countries around the world amid a global shortage that will take years to ease.

A months-long CNN investigation has found that tens of millions of counterfeit and second-hand nitrile gloves have reached the United States, according to import records and distributors who bought the gloves -- and that's just the tip of the iceberg. Criminal investigations are underway by the authorities in the US and Thailand.