A judge has dismissed charges against the wife of a Chinese billionaire accused of taking part in a scheme to steal trade secrets from U.S. corn companies.

The order signed Tuesday instructs the government to return Mo Yun's passport, meaning she can return to China.

Investigators allege that Mo, her brother and five other Chinese nationals were working for a seed subsidiary of China-based DBN Group when they stole seeds from Iowa cornfields and shipped them out of the country in 2011 and 2012.

Prosecutors asked that the charges be dropped against Mo after a judge ruled that investigators couldn't use partial instant messages found on her brother's computer.

Mo's husband is DBN Group Chairman Shao Genhou, who has a net worth estimated at $1.4 billion. He hasn't been charged.