According to witnesses, officers swooped at about 12.30pm on the premises of Immuno Biotech, the company behind the so-called 'miracle cure' product GcMaf.
The operation continued into the evening.
'Law Enforcement Officers have executed a search warrant at a business address in St Peter Port in connection with suspected money laundering offences,' a Law Enforcement spokesman said.
'A number of items have been taken away for further examination.
'Two individuals have been arrested, a female who was at the business premises, and a male who was arrested at a second local address.
'The female has been released on bail pending further enquiries, and the male remains in custody awaiting questioning.'
The investigation is being led by Guernsey's Economic Crime Division, which is a joint Law Enforcement unit.
'Due to the ongoing nature of the investigation, we are unable to give any further details at this time.'
They did not confirm which company had been raided.
The former Health and Social Services Department carried out searches at Immuno Biotech's Lower Pollet premises and a residential property on 28 January last year as part of an investigation into the alleged selling of unlicensed medicines. However, the Law Officers conceded the execution of that warrant had been unlawful.
Items seized have not been returned, but, under the terms of an injunction, the department (now the Health & Social Care) was unable to examine or share the material until a further court order.
In October, Immuno Biotech's David Noakes said he believed the national investigation would never be taken to court.
Guernsey remains the only jurisdiction in the world to ban the import of GcMaf, described by Mr Noakes as a human protein.
Guernsey authorities previously said they would prevent GcMaf importation until a producer could satisfy them it was being manufactured in an environment that was licensed to European standards for medicine production and that it was able to meet the required standards for raw materials in process and end product testing.
They previously added that there was an ongoing criminal investigation being carried out by the MHRA in the UK and by the chief inspector/chief pharmacist in Guernsey, jointly with Law Enforcement.
The Medicines and Healthcare products Regulatory Agency would not comment on the progress of the investigation in October, but said GcMAF products 'may pose a significant risk to people's health and we advise that people do not start treatment with these specific products'.
GcMAF products labelled as First Immune were not licensed medicines, it said, and have not been tested for quality, safety or effectiveness.
Police said this morning that the male is still in custody, pending further enquiries.
Immuno Biotech's CEO David Noakes could not be contacted yesterday.