Police arrested 39 johns and 21 sex trade workers on Calgary streets during a recent sting. (CBC)A two-week investigation into prostitution on Calgary's streets has resulted in dozens of charges, say police.

Police arrested 39 johns and 21 sex trade workers during a blitz from Jan. 27 to Feb. 4. A total of 64 sex trade-related charges were laid and police arrested nine people wanted on outstanding warrants, said Staff Sgt. Colin Adair on Tuesday.

Police also seized 25 vehicles from alleged johns valued at more than $360,000, including luxury vehicles.

Calgary police have seized 258 vehicles since changes to the Alberta Traffic Safety Act allowed the move to come into effect in late 2006.

The vast majority have since been returned, said Adair, because the person was found not guilty, given a discharge or agreed to an alternative measures program. Otherwise, the vehicles are auctioned off, with the money going to the province.

Calgary police's vice unit periodically runs such stings, he said.

This one focused on several known strolls, including parts of Third Avenue S.W. and 17th Avenue S.E.

But prostitution in Calgary is changing, Adair said.

"Years ago street prostitution was a lot busier than what we are seeing now. It still has a big affect on the communities, but it's changing. There's a lot more indoor prostitution. There's a lot more behind closed doors - bawdy houses. Internet is a big part of it."