The Asian nation, the world’s largest commodity importer, bought American corn for shipment in the fourth quarter, according to people familiar with the matter who asked not to be identified because the deals are private. Crops for the fall harvest are currently just being planted and traders estimate sales to China were at least 1 million metric tons.

China is rebuilding its hog herd faster than expected after a deadly pig disease shrunk animal numbers in the past few years. The rebound is fueling demand for corn to feed the animals. As the nation restores pork output with more modern agriculture practices, backyard farmers are being replaced by professional operations known as hog hotels, which usually feed more grains to pigs instead of table scraps. There’s also speculation China is stockpiling crops.

U.S. exporters have already sold more than 20 million tons of corn to China for delivery this season, an all-time high, according to data from the U.S. Department of Agriculture. The agency hasn’t yet published data for any deals for next season, but it’s possible that some may have already been concluded and haven’t been reported.

The surge in demand for U.S. supplies comes as dry conditions threaten crops in Brazil. The two nations are No. 1 and 2 for global corn shipments. While China doesn’t often buy large amounts from Brazil, the situation is still tightening the global supply picture. Importers typically turn to South America for supply during the next few months before the U.S. harvest starts in the fall.

China is forecast to import 28 million tons from all countries in the 2020-2021 season, the USDA’s Being office said in a report this week. While purchases are expected to drop to 15 million tons the following year, it’s still double a quota set by the World Trade Organization that allows firms in China to import the grain at a lower duty rate.

—With assistance from Niu Shuping.