Illinois is getting tougher on those involved in human trafficking and forcing the vulnerable into prostitution.

Gov. Pat Quinn signed a law Saturday that strengthens the ability of prosecutors to target those behind what he called "a tragic trade."

The measure also offers greater protection to the victims, who are often from vulnerable groups like runaways, abused children and immigrants.

Among other changes, the new law expands the definition of "serious harm" to include non-physical forms of coercion, like psychological intimidation or withholding a passport to keep someone in servitude.

It also lengthens the statute of limitations for prosecuting those who exploit minors.

The National Human Trafficking Resource Center says Illinois generates the fifth highest number of calls to its hotline.