Four more people have been sent to federal prison is part of a crackdown in Florida on pill mills that illegally distribute powerful prescription painkillers like oxycodone.

The sentences were part of Operation Oxy Alley that targeted pain clinics in Broward and Palm Beach counties.

Prosecutors say the clinics illegally distributed 20 million oxycodone pills and made some $40 million between 2008 and 2010.

Among those sentenced Friday was 30-year-old Christopher Paul George, who operated the pain clinics along with his twin brother Jeffrey George. Christopher George got more than 17 years in prison. Jeffrey George previously received a sentence of more than 15 years.
In all 28 of 32 people charged in the case have pleaded guilty.

New government figures show Florida's pill mill problem may be easing.