Sheriff Jim Anderson and Santa Barbara District Attorney Thomas Sneddon said in a statement that documents leaked are covered by Judge Melville's Protective (gag) Order.
"We consider the release of these materials to be a violation of the law," the statement said. "Some media commentators have alleged that we are responsible for these leaks. We are not. These accusations are irresponsible, unfounded and untrue."
The officials said they are investigating the matter.
ABC News reported testimony from sealed transcripts of grand jury testimony given by Jackson's accuser. The network has not said how it obtained some 1,900 pages of grand jury testimony, E! Online reported.
Jackson, charged with 10 felony counts, including child molestation and conspiracy, has pleaded innocent. Jury selection for his trial is to begin Monday.