WASHINGTON (CNN) -- Complaints about potential mortgage fraud are up during the subprime mortgage crisis, and the FBI has opened criminal investigations of 14 companies related to subprime mortgage loans, the agency said Tuesday.

The FBI is examining 14 companies for possible fraud in the wake of the subprime mortgage crisis.

The FBI did not identify the companies.

Neil Power, chief of the FBI economic crimes unit, attributed the increase "to good old-fashioned greed."

"On insider trading, we're looking in some cases at whether executives were aware that the value of their holdings would be going down and the executives traded on that information," said Power.

"On accounting fraud, we're looking at housing developers who may have reported cash reserve accounts to reflect falsely inflated values," he told CNN.

Power and other senior officials said the number of suspicious activity reports they review for potential investigation skyrocketed from 3,000 in fiscal year 2003 to about 35,000 in 2006, to 48,000 in 2007. And in the first quarter of fiscal year 2008, Power said, officials have already received 15,000 such reports, putting them on pace to receive 60,000 complaints this year.

The FBI said it investigates only cases involving losses of $500,000 or more, and last year 56 percent of all cases had losses of more than $1 million. The number of pending cases swelled from 800 in fiscal year 2006 to 1,200 in 2007.

Kenneth Kaiser, FBI assistant director for the Criminal Investigative Division, said the FBI has developed an initiative focused on subprime mortgage loan fraud and is working with investigators from other federal agencies.

Officials identified the states that are the "top 10 mortgage fraud hot spots" as California, New York, Texas, Florida, Georgia, Utah, Illinois, Indiana, Ohio and Michigan. E-mail to a friend