The owner of a Massachusetts leather company ran a "sweatshop" operation employing upward of 350 illegal immigrants — paid $7 an hour — in order to fulfill $91 million in Army contracts to supply GI backpacks, federal officials said.

The owner of the New Bedford-based company, Michael Bianco Inc., and three plant managers were charged with recruiting illegal aliens and providing them with false documents that allowed them to live and work in the U.S.

More than 300 federal agents swarmed the plant Tuesday, detaining between 300 and 350 illegal workers, many of whom tried to flee into the surrounding streets as a Coast Guard helicopter monitored the raid overhead. Bitter cold temperatures forced many to return to the plant, said Bruce Foucart, Immigration and Customs Enforcement special agent in charge.

Many of the detained illegal workers were women from Central America. About 100 children were left stranded at schools and day care centers after their parents were rounded up.

Corinn Williams, director of the Community Economic Development Center of Southeastern Massachusetts, estimated about 100 children were left with baby sitters or caretakers.

"We're continuing to get stories today about infants that were left behind," she said Wednesday. "It's been a widespread humanitarian crisis here in New Bedford."

The state Department of Social Services was working Wednesday to make sure the children receive proper care. Department of Homeland Security Assistant Secretary Julie Myers said eight pregnant women were released and women who were sole caregivers of children would also be released, but it takes time to verify people's accounts.

Francesco Insolia, 50, who owned the plant and three managers were changed with helping workers get false documentation to live and work in the United States. The company not only hired illegal immigrants, but courted them in a quest for cheap labor to maximize profits from million-dollar military contracts, federal officials said.

U.S. Attorney Michael J. Sullivan alleged the plant was a "sweatshop" where workers were docked 15 minutes pay for every minute they were late and were only allowed to use the bathroom for 2 minutes or else they would face a $20 fine. Fines were also given for talking during work and for leaving before being told to. Violating any rule twice would get a worker fired, Sullivan told the New Bedford Standard-Times.

Only one roll of toilet paper was provided in each rest room stall per day. Workers were paid $7 to $7.50 an hour, he told the Standard-Times.

"The way the environment is described it's the type of sweatshop that you read about in terms of the turn of the century," Sullivan told the Standard-Times. "I'm not talking about the 21st century, the turn of the 20th century, very early 1900s. These are the deplorable conditions that these workers essentially had to endure under.

"They were given no option, certainly," he continued. "It's either here or the risk of no income. The conditions were horrible. Clearly, they were exploited because of the fact that they are here illegally."

Insolia's wife, Suzanne Thompson, said Sullivan's characterization of the company as a sweatshop was "horrifying."

"None of that is true," she said.

Insolia sent employees to a record shop across the street where they would get false documents. Luis Torres, 45, who worked at the music store, was accused of producing counterfeit green cards and Social Security cards for workers.

An undercover special agent with ICE posed as an illegal immigrant from Mexico and worked undercover at the plant for four days in September 2006. The overall investigation, which began with an anonymous tip from a legal employee who is now a cooperating witness, lasted 11 months.

Michael Bianco Inc., founded in 1985, specialized in manufacturing high-end leather goods for retailers including Coach Inc. and Timberland Co. before landing a $9.4 million military contract in 2003 to make survival vests.

Between 2004 and 2006, it won $82 million in military contracts to make products including lightweight backpacks. An Army spokesman did not return a call about the status of the contracts.

The contracts led to a massive expansion of the company's work force, which grew from 85 employees in 2003 to more than 500, according to investigators.

The Associated Press contributed to this report.