The FBI was investigating Josh Powell for child pornography at least 17 months before he killed himself and his children, according to a published report based on FBI documents.

The Salt Lake Tribune reported that the bureau was investigating Powell for possession of child pornography as well as for the death of his wife, Susan, who disappeared in 2009 and has never been found. 

Anne Bremner, an attorney for Susan Powell's parents, said the family was never told the FBI was investigating Josh Powell for child pornography. If the state of Washington's Department of Social and Health Services had known about the suspected child pornography, it "never would have let him have those kids," she said.

Powell, who had visitation rights, died along with his two sons, 7-year-old Charlie and 5-year-old Braden, on February 5, 2012. After a Washington state worker dropped the boys off at Powell's rented home in the town of Graham, Powell locked the worker out and ignited a fatal fire. 

Josh Powell had been previously linked to child pornography, the Tribune reported. At hearings in the state of Washington to determine custody of his children, then-Assistant Washington Attorney General John M. Long said Powell was under investigation for child pornography after cartoon images of incest between mothers and children were found on his computer in late 2009 or early 2010.

Long, who has since retired, told the Tribune that neither the FBI nor local law enforcement officials told him about any other images or any ongoing investigation. The documents seen by the Tribune do not specify any images or what they showed or depicted. 

The Associated Press contributed to this report.