Eight workers are accused of stealing 55 tons of nickel from a Chester County factory, costing the company nearly $1 million in losses.

The Chester County District Attorney's Office said Wednesday that the employees took the nickel from the South Coatesville factory of ArcelorMittal, an international steel and mining company, between March 2012 and January 2013. They resold the metal to make money, according to prosecutors.

During that period, the group stole a total of 110,704 pounds, or 55 tons, of nickel from the factory, costing the company about $911,000, prosecutors said.

"The most difficult crime to stop is an inside job," District Attorney Tom Hogan said in a statement. "The conspirators knew exactly how to evade detection while carrying out their crimes."

Facing felony theft charges are three former ArcelorMittal employees; two who worked for Vandenburg, a company that supplies maintenance services at the factory; two who were employed by the security company AlliedBarton; and the brother of an ArcelorMittal worker. All except the brother worked at the South Coatesville site.

The ArcelorMittal workers charged are: Dane Douglas, 39, of Atglen; Aaron Anderson, 36, of Coatesville, and Richard Cooper, 54. The Vandenburg employees charged are: George Glassco, 56, of Mountville, and Jeffrey Shuler, 55, of Honey Brook. The AlliedBarton workers charged are Maurice Dennis, 26, and Marcus Pearce, 25, both of Coatesville. The brother who was charged is Corey Douglas, 36, of Lancaster.

The scheme began to unfold in January 2013, when a plant manager saw Glassco shoveling nickel briquettes into buckets, according to court documents.

"There is no legitimate reason for employees to remove nickel briquettes into buckets," a criminal complaint says.

Investigators determined that the group would have sacks of nickel moved to areas of the factory where it would be accessible for theft, prosecutors said. They would then allegedly use backpacks, private vehicles, and a box truck to get the nickel out of the facility and resell it at PASCO, a metal recycling company in Philadelphia.

PASCO's records showed that each defendant received tens of thousands of dollars from the company for nickel sales and cash advances, court documents said. Those payments allegedly totaled $169,981.98 for Dane Douglas, $145,861.98 for Anderson, $77,440.25 for Glassco, $31,480 for Cooper, and $12,000 for Corey Douglas.

Shuler, Dennis, and Pearce all received unspecified sums for not reporting and for helping cover up the thefts, documents said.

All of the defendants have been arrested except Cooper, who is in Texas and expected to be extradited or turn himself in, prosecutors said.