Electoral authorities have launched a formal investigation into the funding and use of a private plane by One Nation.
Australian Electoral Commissioner Tom Rogers late on Thursday night confirmed the matter had advanced beyond an inquiry earlier in May.
He told a Senate estimates hearing the AEC had issued notices to "several" people requesting certain information.
If they do not comply, they could be in breach of the law.
"Now that matter has to play out," Mr Rogers said.
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"We actually have to piece together what is quite a complex issue and only when that is concluded the delegate will be able to make decisions about what the next steps are."
One of those steps could be to refer the matter to another agency for further action.
One Nation leader Pauline Hanson regularly uses the plane - often flown by her chief of staff James Ashby - to visit electorates in Queensland.
But there's been confusion as to who owns it and how it was acquired.
Senator Hanson insists the Jabiru aircraft, which bears her image and the party logo, was not a gift from property developer and party donor Bill McNee.
Mr McNee bought the plane and has allowed Mr Ashby to use it, she told Sky News on May 1.
Meanwhile, Mr Rogers confirmed the AEC believes One Nation has not breached any Commonwealth electoral laws after a preliminary review of leaked recordings of Mr Ashby.
It has been alleged the party sought to defraud money from Queensland electoral authorities using inflated receipts.
"As far as I'm aware, there are no offences against the Commonwealth Electoral Act that have been disclosed by those actions," Mr Rogers said.
"That doesn't mean there won't be other Commonwealth offences under other laws."
The Australian Federal Police and Electoral Commission of Queensland are believed to be evaluating the claims.
