The Land Transport Authority (LTA) has called up four major motorcycle dealers for separate meetings over the recent spikes in motorcycle certificate of entitlement (COE) prices.
The Straits Times understands that the dealers are one authorised agent and three parallel importers.
The LTA would not reveal more, although industry players said the four could be suspected of speculative trading of COEs.
In response to queries, an LTA spokesman merely said: "LTA is meeting some of the major motorcycle dealers to better understand the recent trends in COE prices and motorcycle purchases."
Motorcycle COE prices have been rising from below $2,000 in 2013 to breach $6,000 in 2015. In the past year or so, it has been hovering around $6,500.
In February, the Government imposed additional taxes on higher- end motorcycles in the hopes of dampening big-bike demand - which was seen as one of the causes for soaring motorcycle COE prices.
But instead of falling, premiums shot up further, ending at $7,483 in the first bidding of March, and $8,081 in the second.
Experts have said the higher taxes do not dampen demand, but merely shift demand for high-end bikes to less expensive models. Others said the transferability of motorcycle COEs gives rise to a degree of speculation, which leads to price rises.
Dr Walter Theseira, an economist and senior lecturer at the Singapore University of Social Sciences (SUSS), said: "This situation highlights a basic problem with the motor market - the excessive power that dealers, both motorcycle and car, hold in a small industry where large players account for a huge fraction of the market, and where supply is limited by policy.
"Policymakers do not have enough power or mandate to look more seriously at how to curb their market power."
Another reason for the premium spikes could be corporate demand. The increasing popularity of food delivery services could mean companies are expanding their fleets, said SUSS transport researcher Park Byung Joon.
"This disruption is similar to how car COEs were affected by demand from private-hire car fleets," he said.
However, while Foodpanda's fleet increased from 2,500 at the end of last year to 3,000 currently, the majority of its riders use their own motorcycles, said a spokesman for the food delivery service.
Mr Rex Tan, a spokesman for motorcycle rental firm Ban Hock Hin, said that while his company does supply motorcycles to corporate clients, it does " progressive bidding" over two to three months "so as not to affect prices".
Motorcyclist Keith Tay, 52, suggested that to remove the influence of corporate demand, commercial motorcycle COEs be moved to another category, similar to how taxis were removed from the quota for Category A cars in 2012.
This could help keep prices down, said the real estate agent. "Now, motorcycles are too expensive for the normal rider," he said.
Meanwhile, the Singapore Motorcycle Trade Association said it is concerned that the LTA might modify policies based on the feedback "of a select few".
"It is strange that they did not engage the association," said an association committee member.
"We hope that they won't take what the selected dealers said as a consensus."