A Lawrenceville company that was a major source of classroom paper orchestrated an international conspiracy to reap huge profits by illegally importing low-cost products from China, federal authorities say.

Two executives of Apego Inc., one of whom pleaded not guilty Monday, are accused of being part of an illegal operation that falsified records and bribed officials to make it appear that the company imported paper from Taiwan rather than its true source: China. Prosecutors say the scheme was only uncovered after a fired secretary — who happened to be the chief executive’s ex-lover — turned over a laptop hard drive to Department of Homeland Security investigators.

The federal charges, which contend the company skirted more than $20 million in customs duties, is the latest sign of a crackdown on foreign bribery that has yielded settlements against brand-name companies.

Tyco International agreed in September to pay nearly $27 million to resolve federal charges that some of its foreign subsidiaries bribed officials of foreign governments, then misreported the payments. And the Justice Department has launched an investigation into allegations that Wal-Mart’s Mexican subsidiary bribed officials to secure building permits.

On Monday, Apego’s phone at its Gwinnett County office was disconnected and an employee at a Texas office declined to comment.

At the federal courthouse here Monday, Jennifer Chen, 44, once Apego’s chief financial officer, pleaded not guilty. After handing over a $25,000 cashier’s check and surrendering her passport, the Snellville woman was released on bond.

Her ex-husband, Chi-Cheng “Curtis” Gung, president and CEO of Apego, did not appear for the arraignment. The 45-year-old Snellville man is in Taiwan being treated for what has been described as a potentially grave medical condition and wants to surrender next month, Assistant U.S. Attorney Brian Pearce said.

Also indicted are three affiliates of The Watanabe Group, a company based in China; Zuoru He, a 66-year-old Chinese executive who is the controlling shareholder of The Watanabe Group; and Chong-Sien Wu, a 69-year-old Taiwanese man who founded Apego.

Neither He nor Wu attended Monday’s arraignment. Prosecutors issued warrants for their arrests.

U.S. law imposes steep duties on paper products made in China to discourage “dumping,” the practice of saturating the market with cheap foreign-made goods to drive domestic manufacturers out of the market. “Anti-dumping” duties are imposed on imported merchandise that is likely to be sold in the U.S. at less than its fair market value.

The Commerce Department began an anti-dumping crackdown on Chinese paper products in 2006 by increasing duties for lined paper, such as that used in school loose-leaf notebooks. The value of paper products imported from China plummeted from $645 million in 2007 to $487 million last year, according to trade data. But the U.S. does not impose anti-dumping duties on paper products made in Taiwan.

Enter Apego, a company that was fast becoming a major source of paper products for office-supply companies and large retailers. It opened offices in Taiwan, China and Mexico, and conducted business mostly under the brand name Aclor.

To keep prices down, prosecutors said, Apego and others charged in the scheme bought notebooks and other paper products from The Watanabe Group in May 2006 and then made it look as if the products were made in Taiwan.

They initially did this by hiring temporary workers in Taiwan to put “Made in Taiwan” labels on container-loads of paper that were actually manufactured in China, according to the indictment. But as back-to-school orders soared in 2007, authorities said Apego bribed Taiwanese officials to allow the labels on containers and boxes, sometimes removing Chinese labels.

All told, prosecutors say the scheme allowed hundreds of cargo loads of paper products made in China that would have been slapped with anti-dumping duties of at least 76.7 percent. U.S. Attorney Sally Yates estimated the anti-dumping duties at more than $20 million.

Prosecutors say the company’s executives were at times brazen in their scheme. They said Apego’s leaders attended an International Trade Commission hearing in Atlanta in June 2006 about the anti-dumping duties and, while here, made plans to continue the scheme.

The conspiracy continued into 2007 and occurred so frequently that one employee said in an email, “everybody is overwhelmed from being so busy making fake documents,” the indictment said.

In September 2007, the indictment said, Taiwanese customs officials stopped a shipment of 68 containers and began asking questions about the true origin of the paper products. This led a Taiwan-based Apego employee to suggest the company would make a “significant contribution” to local regulators if it was spared a hefty fine. When the employee got off with a warning, the indictment said, he sent an email to Chen that said: “Case closed…. Yay!”

Investigators learned of the case after Gung’s executive assistant, identified only as A.C. in the indictment, was fired in early 2008, taking with her a hard drive loaded with sensitive data. Prosecutors say Apego’s leaders urged employees to stake out A.C.’s apartments, but their efforts to retrieve the computer failed.

“Their efforts to illegally increase profits not only cheated the U.S. government out of tens of millions of dollars, they also gained an unfair advantage over other companies that play by the rules,” said Brock Nicholson, who heads the federal Immigration and Customs Enforcement office here, which helped investigate the case.