A Chicago Police internal investigation has been opened into the serious injuries that an officer suffered last week during a SWAT training session, a department spokesman confirmed Wednesday.

On Monday, police spokesman Anthony Guglielmi said he couldn’t say whether a formal complaint was opened about the incident. He said the officer was interviewed and “did not allege any impropriety or wish to file any complaints against instructors or students.”

On Wednesday, after a source told the Chicago Sun-Times that an investigation was opened, Guglielmi confirmed, “Yes, there was a complaint, but not by the injured officer. The whole thing will be investigated.”

The source didn’t say who filed the complaint to open the investigation into the training incident.

Guglielmi said the officer was treated at Northwestern Memorial Hospital for injuries that included “a cracked rib.” He noted that the training session in which the officer was hurt was videotaped.

“The video was also reviewed and did not show any obvious improprieties. In all cases, incidents of workplace injury are investigated thoroughly,” Guglielmi said.

The incident has been the subject of angry discussions on an independent blog for Chicago cops. Many of the commenters have blamed a SWAT sergeant for the officer’s injuries.

The sergeant had served in the Army’s special forces in Afghanistan and Iraq, according to his own social media postings.