© PAThe database, located on an Amazon server, did not utilise password protection, meaning it could be readily accessed by members of the public.
Questions are being raised after an unsecured database containing the contact details of almost 50 million Instagram users was found online.
The database was discovered by an Indian researcher, who then contacted US technology news outlet TechCrunch, the BBC reports.
The personal details of multiple Instagram influencers, including celebrities and food bloggers, were also found on the database, as were estimates of each account's commercial worth based on details such as the number of followers and the account's engagement.
The database, located on an Amazon server, did not utilise password protection, meaning it could be readily accessed by members of the public.
It has been linked to a Mumbai marketing company called Chtrbox.
It is unknown how Chtrbox was able to obtain the information to begin with.
The Facebook-owned Instagram is currently investigating.
"We're looking into the issue to understand if the data described - including email and phone numbers - was from Instagram or from other sources," Instagram said in a statement.
"We're also inquiring with Chtrbox to understand where this data came from and how it became publicly available."