The beleaguered Chicago agency that investigates police-involved shootings made no mention in quarterly reports in recent years of dozens of incidents in which officers fired their weapons and had no records at all of six shooting incidents, the city's inspector general found in a report released Tuesday.

As the city, the Independent Police Review Board and police department struggle to regain public trust shattered by the video of an officer fatally shooting black teenager Laquan McDonald, the report raises more questions about what the public is being told -- and not told -- when officers use force.

"During this historic moment of transformation of police oversight in Chicago, the City should recognize that the use-of-force reporting is a crucial tool for meaningful transparence," Inspector General Joe Ferguson's office concluded in the report.

But IPRA suggested the inspector general was unfairly singling it out, saying the agency doesn't have the resources to do much beyond rely on the Chicago Police Department for information about use-of-force incidents.

In a letter to Ferguson, IPRA chief administrator Sharon Fairley acknowledged that IPRA's "historical failure to take reasonable steps to validate the accuracy of the data was problematic," but since she took over late last year the agency has "developed a detailed system for recording an maintaining records related to the data published in its quarterly report."

"We can only report about what the Police Department notifies us about," IPRA spokeswoman Mia Sissac said Tuesday, adding that the department reported, though was not required to report shooting incidents in which no one was struck.

The Police Department did not immediately return calls and an email for comment. Mayor Rahm Emanuel's office forwarded a letter to Ferguson in which his chief of staff wrote that the city is "in the process of overhauling its police accountability structure."

The report revealed discrepancies in the reporting of incidents in which someone was shot, in which nobody was hit, and in incidents in which officers used Tasers or what is commonly known as pepper spray.

According to the report, IPRA underreported by 49 the number of incidents in which officers fired their weapons but did not hit anyone between late 2007 -- the year IPRA was created -- and 2014. The report also found that IPRA reported 32 fewer incidents in which officers used Tasers than actually occurred from the fourth quarter of 2013 and the third quarter of 2014. During the same period, IPRA reported seven incidents in which officers dispensed pepper spray canisters --a fraction of the 126 actual incidents, according the inspector general.

Also, the inspector general's office concluded that IPRA reported 344 officer-involved shootings in which someone was shot, four more than the actual number of these kinds of shootings.

Sissac said the agency is now trying to find information about the six shooting incidents for which it could not find reports.