“Sausage Party” has grabbed the attention of the film community. Thanks to its $34.3 million opening last weekend, the comedy about a group of grocery products has demonstrated that an animated film can be R-rated and made on the cheap, while still drawing crowds.

Instead of basking in the success, the makers of “Sausage Party” are finding themselves embroiled in a controversy that’s being fueled by anonymous comments on a series of blogs and news outlets. The formula used to deliver the film on time and on budget is now drawing unwanted attention, as animators who worked on the film in Canada are complaining they did not get overtime pay or the screen credits they deserved.

Tech workers for Vancouver-based Nitrogen Studios began to post their complaints over the weekend on online forums, particularly targeting a profile of directors Conrad Vernon and Greg Tiernan that ran last week on CartoonBrew.

Workers on the film, which was produced by Annapurna Pictures and released Aug. 12 by Sony, sent a petition to the movie makers last year protesting against long and uncompensated hours. They said they felt intimidated into remaining on the job, without complaint, for fear they would not be hired for future projects at Nitrogen and potentially elsewhere in the close-knit animation industry.

Annapurna declined to comment. Sony, which distributed but was not involved in production of the film, also declined to comment.

Animators who worked on the project only agreed to speak to Variety on the condition of anonymity, fearing that speaking out publicly could limit their professional opportunities. Some described a hostile workplace where staffers were expected to work overtime for no pay. When staffers tried to leave the job early they were told they would not be credited or were threatened with reprisals.

“People would go in to talk to Greg [Tiernan] or give their notice and there’d be screaming about being blacklisted,” said one animator.

The animator claimed that Nitrogen had no human resources staff so any complaints about working conditions had to be made to line producer Nicole Stine, who is Tiernan’s wife.

“There was no one you could go to,” said the animator. “It was uncomfortable.”

Other animators said they had a pleasant, professional time on the project. They were not unhappy that some staff had been denied credit on the film.

“Artists were expected to get their work done on time and meet their quotas,” said another staffer.

For its part, Nitrogen is hitting back at the allegations.

“These claims are without merit,” said Tiernan. “Our production adhered to all overtime laws and regulations as well as our contractual obligations with our artists.”

Asked about if he knew why there were anonymous posts criticizing the company, Tiernan said only, “We take these things seriously and don’t want to ignore these claims.”

Eventually dozens of staffers signed a letter calling on co-producer and co-financier Annapurna to intercede and make sure they got paid. According to an “uncredited supervisor” writing on CartoonBrew: “When the letter got to Annapurna they stepped in and saw that artist were payed [sic] and fed when overtime was needed.”

Still, those commenting online suggested that many who left the production early did not receive credit. While IMDB lists 83 people under animation, only 47 of those got a screen credit, according to one comment on CartoonBrew.

The dispute is a familiar one to many in the animation business, where an over-abundance of talented labor collides with a paucity of quality jobs.

“This is kind of the typical case where hungry artists are working on projects they care about and then they end up burning free overtime hours,” said Daniel Lay, a one-time animation worker who blogs on the topic under the handle VFX Soldier. “It’s sort of almost an accepted practice at the end of the day. A lot of it has to do with the fact that this is an industry of passion. And people don’t want to complain out of fear they won’t get the next job.”

Said one former worker who asked not to be named: “The problem is real. It exists and it’s serious, but at the same time, a lot of jobs are at risk, so we have to be careful what we say.”

The highly trained workers who make animated films have union representation in Los Angeles through IATSE Local 839, the Animation Guild. But in Canada and much of the rest of the world, the workers are not organized.

“A lot of people are very hesitant about speaking out about problems like this,” said Jennifer Moreau, vice president of Unifor Local 2000, which represents other media workers in Vancouver. “There is a huge fear about being blacklisted. Who would hire someone who is complaining about working conditions and unpaid overtime? But it’s unfortunate because there isn’t going to be any change made unless people come forward.”

Because they are temporary, contract workers, animators constantly worry about their next job, Moreau said. “It’s like you are on this perpetual probation period,” she said. “There is no job security.”

Moreau said there are high hopes by union organizers in London that they will soon be able to form a union among animation employees at MPC (Movie Picture Company) in London. “That would be a game-change for the industry,” Moreau said.

Some in the animation business said the problem of work being shifted outside the U.S. to underpaid workers has been exacerbated in Canada by government subsidies that can cut the cost of production by more than half.

Activists on the issue, like the blogger Lay, have supported U.S. tariffs on foreign-made films equivalent to the tax benefits received overseas. “It would lead to better competition in the industry if they didn’t have the benefit of those subsidies,” Lay said.

But proposals for tariffs have not gained traction in what remains a mostly anti-protectionist trade regime in Washington.

As one animator on “Sausage Party” told Variety, “This is the nature of the job. You go all over the world to different cities, trying to find the next job.”