The AFP said on Wednesday afternoon the investigation was ongoing and that no further information was available at this time.
Mr Thomson, was the national secretary of the Health Services Union from 2002 until the 2007 federal election, when he was elected to represent the seat of Dobell on the Central Coast.
The Labor Party suspended Mr Thompson in 2012, while he was an MP, after he was accused of misusing union funds while he was an HSU official.
The Federal Court later found he had spent tens of thousands of HSU members’ dollars on sex workers and his own political campaign.
Mr Thompson ran again for Dobell as an independent in the 2013 federal election, but secured just 4 per cent of the primary vote.
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