The Serious Fraud Office (SFO) has completed a series of raids, in conjunction with local police, on several brokers in Northern Ireland and England in connection with an alleged £3.5m public liability insurance fraud.
A Police Service of Northern Ireland (PSNI) source confirmed that local broker Laing & Co was one of the firms raided.
A Laing & Co spokesman said Laing & Co's offices, as well as the home of Laing & Co managing director Stuart Laing, had been searched.
"Police have raided Laing & Co's offices and Stuart Laing's home. Stuart Laing is livid and is currently consulting his lawyers," said the spokesman.
The SFO confirmed similar raids had been carried out in South Yorkshire and Leicestershire, but would not reveal the identity of the brokers involved.
But the SFO did say Preston Whiteside, Preston Whiteside Underwriting and Preston Roberts were involved in the probe.
A PSNI statement said: "Police inquiries indicate at this stage that as much as £3.5m in premiums could have been lost and the potential exists for the consequent uninsured risk to reach £1bn."
PSNI detective chief inspector Larry Cheshire said: "It is entirely possible that some business people throughout Northern Ireland are not insured for public or employers' liability, even though they have paid premiums and, in some instances, have even received an insurance certificate."
The SFO said no arrests had been made as yet.
Last month it was revealed that Preston Whiteside was being sued for around £1m by Laing & Co.
Laing & Co has obtained judgment against Preston Whiteside and an order for an interim payment of £160,000 has been made by the High Court.