Nitrous oxide is used in whipped cream dispensers as well as by dentists.
The companies will be asked for an explanation before Tukes decides whether they should be allowed to continue to sell to private individuals. One firm has already responded to the request for information, and a decision is expected on the company later this week.
Tukes met with various official bodies to discuss the matter on Tuesday. Parliament is also considering legislation to restrict sales of laughing gas, while any new chemicals law would be overseen by Tukes.
While the use of nitrous oxide for recreational purposes has been known since at least the eighteenth century, there has recently been a resurgence in its popularity among young people in the UK, US and elsewhere. Health officials warn that the chemical, which produces a brief feeling of euphoria, can also cause brain damage and even death.