For years, there has been a battle brewing over the classified website Backpage.com. Advocates have accused the site of facilitating illegal sex trafficking of women and children, and the site has argued that attempts to control it are akin to government censorship.

But on Monday, Backpage’s owners voluntarily shut down its adult section, just as a Senate panel released a report accusing the site of filtering out key words in ads that would indicate child-sex trafficking.

Bradley Myles — the CEO of the Polaris Project, the leading non-profit group that works to fight human trafficking in the U.S. — said that they have learned about more than 2,000 likely cases of sex trafficking involving Backpage on the National Human Trafficking Hotline.

Myles says the Senate panel investigating this found 400 cases in 47 states.

Even as Backpage shut down their adult section on Monday, the owners of the site released a statement saying the decision "should be understood for what it is: an accumulation of acts of government censorship using extra-legal tactics."

Backpage’s owners also said in their statement that closing their adult section won’t reduce human trafficking.  "Instead, it undermines efforts by Backpage to cooperate with law enforcement and provide information to identify, arrest and prosecute those who engage in human trafficking," they said.

Eric Goldman, a professor of law at Santa Clara University in California, has been writing about Internet law and user-generated content sites like Backpage for years.

Her said there’ve been a number of lawsuits against Backpage by government agencies and victims of human trafficking, and Backpage has had a series of victories in them. He says it’s all based on a law called Section 230, which basically says that websites aren’t liable for third-party content that’s posted on them.

Backpage’s owners also posted statements Monday from supporters who also see these as government attempts to stifle free speech.

Dr. Lois Lee, founder and president of Children of the Night, said in a statement that "it's a sad day for America's children victimized by prostitution."

She said that shuttering its adult section dismantles vital resources that helped rescue children from lives in prostitution, including investigative tools depended upon by America's vice detectives.

You can read the full statement from Backpage.com.