America has a severe arson problem, but most Americans do not know it because the reporting system for deliberately set building fires is so chaotic and patchwork that most arsons are not reported to the federal government.

The National Fire Incident Reporting System NFIRS, the world's largest annual database of fire incident information and part of the Department of Homeland Security, monitors local departments' arson reports. The group says 5 percent of all residential building fires are intentionally set.

But a Scripps News investigation, Arson in America, reveals that the rate is significantly higher and that most acts of arson in America are not reported to the federal government.

Scripps obtained records of arsons from nine of the largest cities in the country to compare what was reported to NFIRS against what should have been reported. The difference is dramatic.

For example, in 2011:

Chicago reported just 61 building arsons when it had at least 192.

Houston said it had 25 intentional fires when it really had 224.

Indianapolis reported no arsons when it should have reported at least 216.

New York reported 11 arsons instead of the 1,347 it really discovered.

Arson is grossly underreported, says Bill Degnan, president of the National Association of State Fire Marshals. I believe the rate of arson in America is somewhere between 40 percent and 50 percent.

Underreporting of arson masks a major threat to public safety.

Up to half of the 3,000 fire deaths each year should be treated as homicides.

Arsonists may remain at large, free to burn.

Much of the $15.5 billion paid last year by insurance companies and their clients should be contested since arson often involves fraud.

The federal government has paid out more than $4 billion in grants to fire departments to report into the federal database, and there is no penalty for inaccurate information.

The Scripps investigation has discovered that arson is frequently missed by local fire investigators. Scripps obtained records of 1 million building fires reported to the U.S. Fire Administration from 2006 through 2011 and found clear indications that tens of thousands of arsons may be missed each year.