If it was, the product could be off shelves by next week, otherwise tests would be carried out to determine its contents.
Correspondence released to the Herald under the Official Information Act reveals police and Customs warned ministry policy-makers that proposed bans on "legal highs" needed strengthening.
In a letter dated July 29, Police Minister Judith Collins urged Mr Dunne to note the police's desire that analogues of banned cannabinoids be included in the ban.
Mr Dunne listed 16 synthetic cannabinoids as the equivalent of Class C1 drugs for a 12-month period at the beginning of August.
All 43 synthetic cannabis products on the market at the time were removed from shelves.
But manufacturers warned new products would quickly emerge because there were thousands of different synthetic cannabinoids.
To try to combat this, Customs and police wanted all substances e chemically similar to the banned cannabinoids - known as analogues - to be treated in the same manner.
Custom's border protection and enforcement official David Negri wrote to the ministry on July 29 asking for analogue provisions to be included in legislation.
Mr Negri said that if Mr Dunne continually banned new products, "there may be a perception that the new regime is ineffective and lacks credibility".
He said Customs believed an analogue provision could deter manufacturers from importing and marketing new substances to "test" the regime.
However, ministry staff rejected including analogues because of the difficulty and length of time the Government would face in order to prove a substance was an analogue.
Mr Dunne said yesterday the fact he was alerted to Amsterdam Cafe by the Herald was not an indication detection of new products was failing.
"We're not always going to get everything. When we do hear, as in this instance [the Herald] brings it to our attention, we'll act very quickly."
