DALLAS - Police say one doctor was behind hundreds of people illegally having easy access to addictive drugs like hydrocodone.

Authorities swooped in Thursday to shut down Houston clinics they say were prescribing pills illegally at pain clinics in Houston.

"We are alleging they were engaging in organized criminal activity," said Marie Primm, Harris County assistant district attorney. "They were prescribing medication without a medical purpose."

Police said the man behind it all was Dallas Dr. Robert Bishop.

The Harris County District Attorney's office said Dr. Bishop was allowing the clinics to use his name to prescribe pills. The problem was they say he never actually saw the patients and rarely saw their files.

"It's an all cash business," Primm said. "When people come in they pay $60, $70 [or] $80 bucks for one person. They are seeing 50, 60 [to] 70 people in a day."

Those people allegedly then would turn around and sell the pills, going back to a pain clinic for more.

"They could go to as many clinics at they chose, to as many that would prescribe medication and get as many pills as they wanted," Primm said.

There are no laws in Texas to stop what some call "doctor shopping."

"I am very surprised," said Hilton Rogers, one suspect among many arrested Thursday.

But police said the lucrative businesses was one reason Dr. Bishop could afford a nearly $1 million home in North Dallas.