Millions of pounds of provisions, stuffed into three-dozen 747 cargo planes, arrived here from countries around the world in recent months to service Venezuela’s crippled economy.

But instead of food and medicine, the planes carried another resource that often runs scarce here: bills of Venezuela’s currency, the bolivar.

The shipments were part of the import of at least five billion bank notes that President Nicolás Maduro’s administration authorized over the latter half of 2015 as the government boosts the supply of the country’s increasingly worthless currency, according to seven people familiar with the deals.

And the Venezuelan government isn’t finished. In December, the central bank began secret negotiations to order 10 billion more bills, five of these people said, which would effectively double the amount of cash in circulation. That order alone is well above the eight billion notes the U.S. Federal Reserve and the European Central Bank each print annually—dollars and euros that unlike bolivars are used world-wide.

The central bank’s own printing presses in the industrial city of Maracay don’t have enough security paper and metal to print more than a small portion of the country’s bills, the people familiar with the matter said. Their difficulties stem from the same dollar shortages that have plagued Venezuela’s centralized economy

That means Venezuela has to buy bolivars from abroad at any cost.

The Venezuelan central bank’s latest orders have been exclusively only for 100- and 50-bolivar notes, according to the seven people familiar with the deals, because 20s, 10s, 5s and 2s are worth less than the production cost.