BANGOR, Maine — The former manager of a buffet-style Chinese restaurant in Waterville was sentenced Tuesday in U.S. District Court to 14 months in federal prison on conspiracy charges related to the employment of unauthorized workers, according to the U.S. attorney’s office.

Mei Juan Zhang, 31, of Fairfield waived indictment and pleaded guilty in April 2013 to one count each of conspiracy to harbor illegal aliens for commercial advantage and private financial gain, money laundering conspiracy and conspiracy to file false employer’s quarterly federal tax returns.

In addition to prison time, U.S. District Judge John Woodcock sentenced Zhang to three years of supervised release and ordered her to pay more than $54,000 in restitution in unpaid payroll taxes.

Woodcock ordered her to report to prison on May 30. Zhang remains free on $5,000 unsecured bail.

The Zhang family owned buffet-style Chinese restaurants in Brewer, Portland, Lewiston and Waterville, according to court documents. The family also owned five restaurants in Massachusetts and two in Rhode Island.

The investigation, which began in February 2006, revealed that the Zhang organization employed and harbored scores of unauthorized workers at its Chinese buffets and bistros, according to a previously published report. The family allegedly harbored them at 11 safe houses in three states located near the restaurants and ferried them to and from work in vans.

Zhang’s cousin, Mei Ya Zhang, 28, of Brewer, pleaded guilty in June to similar charges related to activities at the Brewer restaurant. Her sentencing date has not been set. She remains free on bail.

Between June 2008 and mid-November 2011, 18 individuals were identified as being in the U.S. illegally and working at the Waterville restaurant, according to the prosecution version of events to which Mei Juan Zhang pleaded guilty. Each was paid at least $1,300 in cash and received no overtime pay, health insurance, workers’ compensation or other benefits. Most worked 12 hours a day, six days a week.

The restaurant also employed some legal workers, according to court documents. They were paid with payroll checks and reported on the restaurant’s quarterly tax filings. The unauthorized employees were not.

The unauthorized workers lived at what was described in court documents as a “safe house” at 7 Oak St. in Waterville. Conditions inside the house were not described, but money was deducted from their pay for housing.

Zhang faced up to 20 years in federal prison on the money laundering charge. On the harboring illegal aliens and filing false federal tax return charges, she faced up to 10 years in prison. In addition, she could have been fined a total of $1 million.

Under the federal sentencing guidelines, she faced between 21 and 27 months in federal prison, Assistant U.S. Attorney Donald Clark said Tuesday after the sentencing. He said that he recommend Zhang be sentenced to the low end of the guideline range.

The prosecutor said that the judge imposed a variant sentence.

Efforts to reach Federal Public Defender Virginia Villa, who represented Zhang, were unsuccessful Tuesday.

The investigation was conducted by the U.S. Immigration and Customs Enforcement’s Homeland Security Investigations division, the Internal Revenue Service, the U.S. Department of Labor, Office of Inspector General, Office of Labor Racketeering & Fraud Investigations, with assistance from the Waterville Police Department, according to a press release issued by the U.S. attorney’s office.

“Homeland Security Investigations is committed to holding businesses accountable when they knowingly hire an illegal workforce,” Bruce Foucart, special agent in charge of the Boston office, said after the sentencing. “Employers who willfully violate our nation’s hiring laws gain an unfair economic advantage over their law abiding competitors. Our goal is to protect job opportunities for the nation’s legal workers and level the playing field for those businesses that play by the rules.”

The Zhang family also owns the New China Super Buffet in Lewiston, which was raided by federal agents in conjunction with raids on the family’s other restaurants.

According to court records, an investigation beginning in 2007 that included surveillance concluded that nine of the restaurant’s workers were illegal and that employees lived at a “safe house” at 36 Pineland St. in Lewiston. They were driven between the residence and restaurant daily in a van.

Authorities determined through audits of bank accounts that the family skimmed $266,000 in cash from restaurant receipts over a 10-month period ending in February 2011, court papers showed.

Mei Juan Zhang was listed as a corporate officer and/or registered agent at the Lewiston restaurant.