The TLC series about two parents raising 8-year-old twins and 5-year-old sextuplets drew nearly 10 million viewers for its fifth-season premiere Monday - more than double the audience for its fourth-season finale several weeks ago following media reports that the parents, Jon and Kate Gosselin, had cheated on each other. They denied it, but conceded their marriage is in trouble.
TLC said Friday it "fully complies" with state laws and regulations.
The Labor Department received a complaint against the show and is "gathering information" from its representatives, department spokesman Justin Fleming told The Associated Press. Fleming would not say when the complaint was filed or who filed it.
The fact a complaint is being investigated doesn't necessarily mean the department believes the show did anything wrong.
"Any complaint we get, we investigate," Fleming said.
Child actors and other young performers are protected by Pennsylvania labor law, but it's not clear whether the law applies to reality TV. Investigators will have to decide whether the Gosselins' house in southeastern Pennsylvania is essentially a TV set where producers direct much of the action - in which case the law may apply - or if it's a home where the kids aren't really working but are simply living their lives, albeit in front of the cameras.
Kate's brother and sister-in-law made waves this week by saying the Gosselins are exploiting their children for financial gain. Jon and Kate Gosselin are reportedly paid tens of thousands of dollars per episode.
"Unfortunately, I think it has come down to all about the ratings," sister-in-law Jodi Kreider told CBS' "The Early Show." "And no one is looking at these children as what they are going through and the life consequences they are going to have as they get older."
Kreider said the children have told her they don't like the cameras.
Her husband and Kate's brother, Kevin Kreider, said in the same interview: "You can't imagine as a child realizing that my birthday party, that all the outings that my parents took me on were ... for ratings, and all organized by production companies."
TLC spokeswoman Laurie Goldberg said in a statement Friday that the network "fully complies with all applicable laws and regulations" for all shows.
"For an extended period of time, we have been engaged in cooperative discussions and supplied all requested information to the Pennsylvania Department of Labor," Goldberg said.
Child labor laws vary by state. Pennsylvania law permits kids who are at least 7 to work in the entertainment industry, as long as a permit is obtained and certain rules are followed. Kids can't generally work after 11:30 p.m., for example, or perform any place that serves alcohol.
The law allows performers younger than 7 to have "temporary employment ... in the production of a motion picture," and spend up to eight hours a day and 44 hours a week on set as long as their "educational instruction, supervision, health and welfare" needs are being met.
In contrast, California has more elaborate rules governing the work of child performers, establishing working hours by age group (20 minutes a day for infants, up to six hours for older kids) and requiring a teacher to be on the set.
"Jon & Kate Plus 8" tapes off and on throughout the year, averaging two to three hours a day, two to three days a week, Goldberg said.
George Voegele, a labor lawyer at Cozen O'Connor in Philadelphia, said the state Labor Department might well decide it doesn't have jurisdiction over the show, especially if investigators determine the cameras are there to document the kids, not direct them.
"The fundamental question I see here is whether or not they're employees, whether they're working, and whether the Pennsylvania child labor law provisions would even apply to this situation," he said.
The Pennsylvania investigation recalls a 2007 controversy surrounding "Kid Nation," a CBS reality show about 40 children given the task of organizing and running their own lives in New Mexico.
The Screen Actors Guild and others suggested the children were being exploited and one trade magazine said the show was skirting New Mexico labor laws by declaring the production a "summer camp." Producers denied the accusations; the show lasted 13 episodes.
Seeking more space for their brood, the Gosselins moved in October into a $1.1 million house on nearly 24 acres with a white picket fence and gated, tree-lined driveway.
A few miles away, in the small town of Wernersville, everyone seems to have an opinion about the sharp-tongued Kate and her long-suffering husband.
Amanda Baez, 32, an assistant at her mother's Wernersville hair salon and an avid watcher of the show, said she's not concerned about the children's welfare.
"This is all the children know, especially the sextuplets since they were babies. They grew up with cameras in their faces. They grew up with the production," she said. "It's probably like having their aunt and uncle with the family video camera just watching you."
AP Television Writer Frazier Moore contributed to this story from New York.
By Michael Rubinkam