The purchases by China, the world's second-largest corn consumer after the United States, come at a time when Beijing has been selling reserves to tamp down rising prices.
Traders and analysts said the purchases were primarily for feedmakers in China, adding there has been no sign yet that the Chinese government was building state stockpiles.
Traders and analysts polled by Reuters estimated imports in the 2009/10 (Aug/Sept) and 2010/11 marketing years to range from 700,000 tons to 6 million tons.
The April 28 purchase was the first by China in nearly four years. There has been speculation that China has bought as many as 15 cargoes of U.S. corn, totaling 825,000 tonnes to 900,00 tons.
"Start of Something"
"Everybody is trying to determine is this just the start of something or is this just getting extra supplies around them a little bit to psychologically cool their prices," said Don Roose, analyst with U.S. Commodities in West Des Moines, Iowa.
Chicago Board of Trade corn futures have been invigorated by China's purchases, which some traders have described as a "game changer" amid prospects for continued sales to Beijing.
Of the total 369,000 tons, USDA said 239,000 tons were for delivery during the 2009/2010 marketing year and 130,000 tons for delivery during 2010/2011.
Any sale of 100,000 tons or more must be reported to the USDA by the next day.
The department also announced export sales of 174,000 tonnes of corn for delivery to unknown destinations, which some traders speculated could be for China.
