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Story highlights

Chicago's 141 homicides were by far the most of the cities surveyed

The agencies also reported combined increases in rapes, robberies, aggravated assaults and non-fatal shootings

(CNN) —  

Homicides across dozens of U.S. cities spiked by 9% over the first three months of 2016 compared to the same period last year, a new report has found.

The report, issued by the Major Cities Chiefs Association on Friday, analyzed crime reported by 63 municipal and county departments from more than 50 cities and metropolitan areas, including New York, Los Angeles, Chicago, Washington and Miami. Combined, the agencies reported 1,365 homicides through March, up from 1,251 over the same period last year.

The agencies also reported increases in rapes, robberies, aggravated assaults and non-fatal shootings.

Chicago’s 141 homicides were by far the most of the cities surveyed, a 70% increase over last year. The Los Angeles Police Department reported 73 homicides, up from 55. The 40 homicides in Las Vegas were nearly double last year’s total.

Not all cities reported increases in homicides, however. New York, for example, recorded 68 homicides, down from 85 the year before.

The MCCA is comprised of police chiefs and sheriffs representing the 68 largest law enforcement offices in the U.S. and was created to discuss common law enforcement issues and ways to solve them in urban areas.

The report comes as FBI Director James Comey has suggested that the filming of police officers, intended to deter police brutality, has altered the behavior of law enforcement.

The “viral video effect,” as Comey called it on Wednesday during a roundtable discussion with reporters, is responsible for “changes in the way police may be acting, and in the way communities may be acting, in terms on how much information they share with police.”

Comey avoided using the term “Ferguson effect” – the notion that police are reluctant to enforce laws proactively for fear of becoming the next bad cop on YouTube – to describe the uptick in crime. Last fall, Comey was criticized for supporting the idea that restraint by cops in the wake of criticism is at least partly to blame for a surge in violent crime in some cities.

The White House pushed back against Comey’s comments on Friday, with Press Secretary Josh Earnest saying it’s “unclear what’s going on” and that there is not a firm answer to the rise in crime.

“This administration makes policy decisions that are rooted in evidence,” Earnest said at a White House briefing. “We can’t make broad, sweeping policy decisions or draw policy conclusions based on anecdotal evidence. That’s irresponsible and ultimately counterproductive.”

CNN’s Eliott C. McLaughlin, Pamela Brown and Evan Perez contributed to this report..