Mexican guest workers filed Wednesday a U.S. Department of Labor complaint against CJ's Seafood alleging the company didn't pay overtime for long shifts, locked them in and made physical threats for not working fast enough.

"If we didn't finish our production quotas, we were told we couldn't take breaks and the manager said while blocking the exit that if we didn't understand that then we would understand 'with a shovel,'" said Silvia Alfaro, 39, among the eight workers who joined in the complaint, representing all of about 40 immigrant temps employed at the business.

A representative of CJ's Seafood, in Breaux Bridge, La., said the company wouldn't comment.

The workers were receiving an hourly salary of $8.53 to boil and shuck crayfish in shifts that started at 2 a.m. Some of the men claim they would come in to boil the catch and then move directly to shucking and packing the shellfish meat, working a 24-hour shift about every three days.

The workers, who are in the U.S. legally under the H-2B visa program, went on strike June 4 after calling the police weeks earlier to complain about poor treatment. After general manager Michael Leblanc learned workers went to the police, the workers claim he made threats against their families back home, saying he knew bad people in Tamaulipas state, where the laborers are from and which has been wreaked with drug-war violence for years. The St. Martin Parish, La., Sheriff's Department responded to the call, but only interviewed the worker who alerted authorities in the presence of the company manager. No further action was taken.

CJ's Seafood is a supplier to Wal-Mart Stores Inc. (NYSE: WMT), the No 1. U.S. retailer.

"This is a particular case because Wal-Mart takes responsibility for their entire supply chain," said Stephen Boykewich of New Orleans-based National Guestworker Alliance. "Lots of companies might say they can't possibly monitor all of their suppliers, but Wal-Mart has built its reputation around doing just that, and if Wal-Mart wants to build their brand around that, then they have to respond to a case like this right out of Louisiana."

Wal-Mart said it is looking into the allegations.

"As soon as we received reports of potential violation of our ethical sourcing policy we launched an investigation," said Megan Murphy, international corporate affairs manager for the Bentonville, Ark.-based retailer. "We take reports like this very seriously and we will take appropriate actions based on the findings from our investigation."

The Department of Labor's Foreign Labor Certification Datacenter said CJ's Seafood was certified for 60 cannery workers from January to July. The company ended up bringing in 40 workers.  

The employees have been living in communal accommodations steps away from the work area, paying $45 a week. They also allege that their freedom of movement was curtailed.

"We were allowed to go to church," said Alfaro. "But we were allowed to go out at night only if we got permission and told them at what time we would return to our quarters."

Many of the employees have been employed by CJ's Seafood for years. It's common in these relationships for seasonal guest workers to return to the same employer every year. While they enter on H2-B visas they're not allowed to resign and work elsewhere. They are at will workers, which means they can be fired and deported (or expected to leave on their own cognizance) for any reason.

When asked why they would return to the same abusive employer, Alfaro said: "It was always bad. This year we couldn't take it any longer, after he threatened our families."

The lawsuit comes in the shadow of a legal challenge from a group of small businesses and the U.S. Chamber of Commerce to the Department of Labor's attempts to bolster what it and labor rights advocates say will increase protections for these workers. They currently pay fees and other costs that often run into the thousands of dollars in order to obtain temporary legal seasonal work in the US.

Lawmakers from both parties, including President Barack Obama and former President George W. Bush, have advocated increasing the number of guest workers. The Congressional Hispanic Caucus and labor rights advocates say the system is rife with abuses, while small businesses that rely on these workers say they shouldn't be collectively punished with stricter regulations on importing foreign temps over the illegal practices of some employers.