Last week, stockbroker Henderson Crosthwaite suddenly resigned as nominated adviser to Alpha Omikron, leaving the firm until the end of the month to find a replacement or face loss of its quotation.
The Stock Exchange is understood to be looking at investors that the firm shared in common with Greenhills, another AIM company involved in restaurants, which collapsed in December.
The Department of Trade and Industry has already launched an investigation into the suspected ring under Section 177 of the Financial Services Act.
Investigators, who have been interviewing City brokers and investors, are seeking to prove links between the alleged ring, a corporate financier at a leading London investment bank and a group of Monaco-based brokers.
Earlier this month officials at the investment bank denied to the Independent on Sunday any knowledge of a parallel inquiry by the Securities and Futures Authority into the affair.
The ring is alleged to have used insider information over 10 years to profit from a number of deals, including BTR's takeover of Nylex and Richemont's acquisition of Rothmans in 1995, as well as plays by Williams Holdings.
Dealings were carried out via Monaco and other offshore havens, including Switzerland and Andorra.
None of the investors or brokers can be named at present for legal reasons. Several of those on the suspect list, however, have been known to the DTI and have figured in at least one other inquiry - that into dealings by a "fan club" of engineering firm Suter in the period from 1984 to1988.
This weekend, Henderson Crosthwaite declined to elaborate on the reasons for its resignation, while representatives of Alpha Omikron were unavailable to comment.
Shares in the company - which also distributes medical products in Russia and has syringe factories in North Korea and Hungary - reached 23p early last year, against its 17p opening price on AIM in December, 1995. On Friday they stood at just 3p.
Last September, AIM brokers Neill Clerk Capital resigned as advisers to Greenhills. The company is now in the hands of receivers at accountants Levy Gee.Reuse content