CHESTER COUNTY , Pa. (WPVI) -- At a news conference on Wednesday, Chester County District Attorney Tom Hogan held some of the highest quality crystal meth that he says has ever been in the region.He says meth is making a comeback thanks in part to dealers like Reuben Vargas Santillan."He is a Mexican national. He is here illegally and he is here selling drugs," Hogan said.Hogan says with heroin use going down, Vargas Santillan has helped create new demand for pure crystal meth in the county.He was arrested after allegedly selling nearly a kilo of the drug to an informant earlier this year.The DA says Vargas Santillan was working directly with Mexican cartels.In fact, he says dealers and cartels have a business model for building demand for meth.Hogan said, "It's like big pharma, they're going to get you using a drug and then they're going to jack the price up once they've got enough addicts and enough people using it."Alongside Hogan at the news conference Wednesday were some members of local law enforcement.That included the chief of the Southern Chester County Regional Police Department, Gerald Simpson.Together they announced the arrests of four other low-level dealers.Chief Simpson says his department has seen a drastic uptick in meth-related arrests.He adds when someone is on the drug their behavior is dangerously irrational.He said, "I'm aware of cases of violence associated to that and it is real to our communities."Hogan says to combat this, his office has numerous investigations going on right now.