Federal officials charged a suburban Detroit restaurant owner and his wife Friday with harboring immigrants who were in the U.S. without legal permission after a fire at a house he owned killed five employees about two weeks earlier.

Roger Tam, 55, was arrested Thursday and appeared Friday in U.S. District Court in Detroit. His wife, Ada Lei, 48, also has been charged, but has not been arrested because she is hospitalized for an undisclosed reason.

Five Mexican nationals lived in the basement of the home owned by Tam in an upper middle-class neighborhood in Novi, northwest of Detroit, while working at Tam's restaurant, Kim's Garden. The Jan. 31 fire has been ruled accidental and possibly caused by smoking; a smoke detector in the basement had been disabled. The basement had stairs to the first floor but windows made of glass block, which would prevent any escape in an emergency.

"He's a really good man," defense attorney Samuel Bennett told reporters after Tam's hearing. "He truly loved those men and boys as his own family."

The Associated Press was unable to determine the name of Lei's attorney to reach out for comment.

The treatment of immigrants who work in restaurants and live together has attracted widespread attention, most recently in the Chicago area, where Illinois' attorney general filed a lawsuit in November to stop alleged civil rights violations in housing and pay. And in Michigan, there are two cases involving farm workers pending in Tuscola and Huron counties, U.S. Attorney Barbara McQuade said.

The Mexican nationals, whom authorities have said were neither U.S. citizens nor in the country legally, were "off the books," McQuade said Friday, meaning they were not listed as employees of the restaurant and no tax documentation was made for them. They are believed to have worked 16-hour days, 6 days a week and been paid about $2,000 a month, authorities said.

"I just want to acknowledge the tragic loss of life," McQuade told reporters at a Friday morning news conference announcing the charges. "I think it's always easy to blame victims in a situation like this where people were in this country illegally, but I think all of our hearts go out to people who died in a very tragic way in a fire."

The men were identified as Brayan Contreras, 16; Leonel Rodriguez, 18; Simeon Nunez, 18; Miguel Diaz, 23; and Pablo Encino, 23. They didn't have their own transportation and relied on Tam to take them to work and bring them back to the home, authorities said Friday.

Homeland Security and other agencies are looking into possible human smuggling and whether there are unsanctioned immigration routes into Michigan.

The charge that Tam and Lei face carries a 10-year prison sentence and a $250,000 fine.

"There is, however, a sentencing enhancement where the conduct results in death," McQuade said. "We're still investigating that aspect of the case, but certainly there's indicators here that that is a sentencing enhancement that we may seek at the appropriate time."

A judge ordered Tam jailed pending a detention hearing on Wednesday.