State labor regulators fined two Ukiah restaurants more than $1.9 million Thursday for alleged wage theft violations over three years.

The violations at Walter Cafe and Ruen Tong Thai Cuisine involved 47 workers and included overlong workdays, failure to pay overtime and the forced falsification of timecards.

The restaurants' co-owners, Yaowapha Ritdet and Steve Walter, have challenged the fine, said Kathleen Hennessy, a spokeswoman for the state Department of Industrial Relations, whose Division of Labor Standards Enforcement investigated the case. A hearing date has not been set, she said.

Ritdet and Walter could not be reached for comment Thursday.

The fine "is one of the larger audits for the restaurant industry," said Hennessy. The investigation is ongoing, she added, leaving open the possibility of additional penalties.

Ritdet and Walter are being held both individually and jointly liable for the alleged Labor Code violations.

Employees at their two restaurants regularly worked at least 11.5 hours a day, six or seven days a week, with no meal breaks, according to a Labor Standards Enforcement division news release. The restaurants did not pay minimum wage or overtime, in violation of the law, according to the agency.

Some of the workers were forced to sign timecards containing falsified information stating they had only worked between five and six hours each day, the agency said. Others were paid in cash with no information on the total hours worked, rate of pay or deductions provided.

Both restaurants were open Thursday. An employee at Ruen Tong Thai Cuisine who answered the phone declined to discuss the case.

The investigation started in June 2012 after an anonymous complaint was filed. It was conducted by state and federal labor regulators and examined employment practices at the restaurants from June 19, 2010, through June 15, 2013.

The 47 workers are due $1,086,436 in unpaid minimum wages, $376,640 in unpaid overtime and $153,582 for no meal period premiums, the agency said. In addition, a total of $189,250 in civil penalties were assessed for wage violations.

"The extraordinary amount of wages assessed at these two restaurants goes to show that if unchecked for too long, wage theft is highly detrimental to workers, and the competitive advantage gained relative to law-abiding employers is significant, harming the entire business community," state Labor Commissioner Julie A. Su said in a statement.

You can reach Staff Writer Jeremy Hay at 521-5212 or