A special commission looking into fuel purchases by the financially troubled electric utility in Puerto Rico has turned over its findings to U.S. federal authorities for further investigation, the majority leader of the island's Senate said Monday.

Officials with the U.S. attorney's office and the FBI spent two days last week picking up material gathered by the special Senate commission in its investigation of the electric utility known by its initials, PREPA, Sen. Anibal Jose Torres said.

Earlier, the commission had submitted its findings to the island's Justice Department.

The special Senate investigative commission has been looking into allegations that the utility overcharged customers by hundreds of millions of dollars while amassing about $9 billion in debt in recent years. Utility officials appearing before the commission denied wrongdoing.

The commission, which has entered the final evidence-gathering stage of its investigation, has found "sufficient information to refer to other branches of local and federal government," Torres said in a statement.

Neither state nor federal authorities have charged anyone involving allegations of fraud raised by the commission and the FBI declined comment on the statement issued by Torres.