CHICAGO – Authorities in Chicago on Thursday showed off eight tons of marijuana they found in a tractor-trailer, saying the drug seizure will help with efforts to combat gang violence in the nation's third-largest city.

"The competition between narcotics dealers for these markets is keen and it results in violence," said police Superintendent Garry McCarthy. "This is not the (violent) crime. This is the driver of the crime and when we make seizures like this, we can affect street level sales ... and it impacts on crime in the city."

Chicago has seen a dramatic increase in homicides this year — up about 50 percent so far when compared with the same period last year — and police blame much of the violence on the city's gangs.