Facebook often stands accused of buddying up to law enforcement and being too quick to turn over user information. However, Chicago police blamed the social media giant this week for dragging its feet during a criminal investigation.

The cops complained that Facebook did not cooperate during a drug and gun-running case involving an invite-only group on the platform. This private group could not be found via the site’s search function, so police turned to Facebook for help. But they didn’t receive assistance, and Facebook even allegedly removed covert profiles set up by investigators.

“Facebook has a responsibility to the people that they serve to ensure that these types of things don’t go on,” police Superintendent Eddie Johnson said. “And quite frankly they haven’t been very friendly to law enforcement to prevent these things.”

However, despite the lack of help from Facebook, undercover officers were able to infiltrate the group and arrest about 50 people while seizing 18 guns. But that didn’t stop the cops from blasting Facebook for its role (or lack thereof) in fighting crime.

“The things that are being trafficked on their site are killing people in Chicago,” said Anthony Riccio, head of the department’s organized crime division. “I think they have an obligation to take steps to make sure that stuff doesn’t happen.”

It’s a fine line Facebook walks between not doing enough to stop criminal activity and infringing on people’s privacy and rights. But it’s the responsibility the site has, and it needs to find a way to better handle it.