Federal authorities seized 14 7-Eleven stores on Long Island and in Virginia early on Monday, charging nine owners and managers with harboring and hiring dozens of illegal immigrants and paying them using sham Social Security numbers, officials said.

Immigration and Customs Enforcement agents and federal prosecutors in Brooklyn were also investigating 40 other 7-Eleven franchises in New York City and elsewhere, in one of the largest criminal immigrant employment investigations ever conducted by the Justice and Homeland Security Departments, officials said.

The franchises split their profits with the 7-Eleven parent corporation, which handles the store payrolls, and prosecutors were seeking $30 million in forfeiture from the stores and the corporate parent. In addition to seizing 10 7-Eleven stores in New York and 4 in Virginia, the authorities seized 5 houses in New York.

The raids come at a time when Washington is embroiled in an intense debate over an overhaul of the nation’s immigration system, including stronger enforcement at the borders and in workplaces.

The charges and two indictments were announced at a news conference on Monday by Loretta E. Lynch, the United States attorney in Brooklyn, and James T. Hayes, who is in charge of Immigration and Customs Enforcement’s office of investigations in New York City, along with officials from the New York State Police and the Suffolk County Police Department.

Through the scheme, officials said, the defendants hired more than 50 illegal immigrants, provided them with more than 20 identities stolen from United States citizens, including children and dead people, put them up at houses owned by the defendants and stole substantial portions of their wages.

“From their 7-Eleven stores the defendants dispensed wire fraud and identity theft, along with Slurpees and hot dogs,” Ms. Lynch said. “In bedroom communities across Long Island and Virginia, the defendants not only systematically employed illegal immigrants but concealed their crimes by raiding the cradle and grave to steal the identity of children and even the dead.”

Ms. Lynch said the defendants “ruthlessly exploited their immigrant employees,” forcing them to live in unregulated boardinghouses and “creating a modern-day plantation system.”

The charges against the owners and managers — eight men and a woman — included wire fraud conspiracy and aggravated identity theft.

Many of those charged were of Pakistani descent and it was believed that most, if not all, of the illegal immigrants were also from Pakistan, officials said.

In one instance, an employee of one franchise was paid using the Social Security number of a former 7-Eleven employee, a person who had not worked for the store for 10 years and who had been the target of collection efforts by the Internal Revenue Service for much of that time because of the reported payments to the illegal immigrant, officials said.

The conduct charged, officials said, had been going on since 2000, during which the defendants generated over $182 million in revenue. Twenty-five of the 40 additional 7-Eleven franchises under scrutiny were to be inspected on Monday as part of the ongoing investigation.

Officials said the parent company lacked enough internal controls to prevent the same Social Security numbers from being used to pay more than one store employee, which happened in more than one instance.

Scott Matter, a spokesman for the parent company, said it was aware of the arrests and seizures and “has been cooperating with federal authorities during their investigation.” Mr. Matter said the company would have no comment until it learned more about the case.

Eight of the nine who had been charged in the indictments were in custody, five of them in New York and three in Virginia, officials said. The last individual was being sought.

One of the raids took place around 6 a.m., at a 7-Eleven on Carleton Avenue in Islip Terrace, on Long Island, according to a law enforcement agent at the scene who declined to give his name or reveal the agency he worked for. One person, he said, was taken into custody from the store and two people were taken away from a house across the street.

A neighbor who lives near the house said it had been divided into several apartments.

“It’s packed in there,” said the neighbor, who asked not to be identified. “There’s been a constant flow of new people coming in.”

Randy Leonard contributed reporting. Read more from the New York Times