Twitter has cut off Geofeedia’s access to its data, in the wake of a report from the American Civil Liberties Union that law enforcement has been monitoring activists and protesters using social media data collected by the startup.

Twitter is following moves from other social media sites: Instagram and Facebook cut off the access it provided to Geofeedia on Sept. 19, according to a post from the ACLU Tuesday.

Representatives from Geofeedia did not immediately respond to Chicago Tribune requests for comment.

Geofeedia makes a platform that lets its clients monitor social media posts and other data tied to a specific location. In February, the company said it had more than 500 customers, including media, corporate operations, marketing and organizations in the public sector.

Denver police provided documents to the Associated Press showing it spent $30,000 for a one-year subscription to Geofeedia. In requesting funding, Denver Police Lt. William Mitchell said it would be used to monitor large events, including Denver's annual marijuana rally and Martin Luther King Day march and parade.

"You are able to see real-time potential threats being made to an event," Mitchell wrote in the funding request, adding that the program assisted in the Boston Marathon bombing investigation and helped police find a woman who made social media threats during Super Bowl festivities. "It has the ability to identify criminal suspects and their actions as they post them to social media."