Chicago Police say they made dozens of arrests after infiltrating an invitation-only group on Facebook where they purchased guns and drugs.
Police say the investigation started when an informant told the department's narcotics division about the Facebook group that couldn't be found through the search function.
Officers began working the case in February, police said, and learned of the group through community intelligence.
In the private group, "sellers posted weapon and drug sale flyers," according to CPD spokesman Anthony Guglielmi.
Once investigators infiltrated the group — an effort that took months, police say— they seized 18 guns and $46,000 worth of drugs. Then they arrested 50 people and secured arrest warrants for 18 more.
But in announcing the nearly yearlong operation on Thursday, Police Superintendent Eddie Johnson harshly criticized Facebook for what he said was the website's unwillingness to help officers at all.
Facebook issued a statement on Thursday afternoon, saying that they routinely work with police to prevent the sale of illegal items.
"We are investigating this report now as it is the first time we've been alerted to it," a spokesperson for the company said. "We do not allow the sale of drugs or guns on our platform. We routinely work with law enforcement and outline how officials may submit a request on our site."
A police spokesman said later Thursday that Facebook has since reached out to the department and that the company and police plan to meet to discuss issues detectives encountered.
Among those arrested, police said, were some with previous convictions.
Johnson said one offender was wanted for attempted murder in Indiana, another sold items through the online group while on electronic monitoring and a third was recently arrested for carjacking and aggravated battery with a firearm, all while being on parole.
“These innovative raids are the latest example of the smart, strategic steps the men and women of the Chicago Police Department are taking to combat gun violence," Mayor Rahm Emanuel said in a statement Thursday. "Whether criminals are operating online or on the street, we will always ensure CPD has the tools, technology, training and talent to track them down. I commend the leadership and rank and file of CPD for their proactive, professional policing that has taken more than 8,600 illegal guns off our streets this year and helped drive a reduction in crime in communities throughout the city.”