Mutual fund firm Fidelity Investments has marked down the value of its share in Snapchat by 25 percent in September, regulatory filings confirmed.

The reduction in the estimated value of Fidelity's stake in Snapchat is the first since the group made an investment in the chat startup earlier in May with a value of $16 billion.

It is unclear if Fidelity made the markdown on its Snapchat investment due to changes in the performance of the company or due to changes in the condition of the broader market. Spokespersons for Fidelity and Snapchat refused to issue a comment on the matter when contacted by the Wall Street Journal.

Snapchat, based in Los Angeles, has been able to raise over $1 billion in funding rounds, with investors ranging from venture capital firms such as Kleiner Perkins Caulfield & Byers and Benchmark, hedge-fund Coatue Management and Asian tech companies such as Tencent Holdings and Alibaba Group Holding. Fidelity is Snapchat's sole mutual fund investor.

Mutual funds need to report on the value of their holdings every quarter, with the firms varying in their process of assessing the value of private startup companies such as Snapchat partly due to the fact that these companies do not usually release detailed financial performance reports. An analysis by the Wall Street Journal on tech startups that have a value of over $1 billion saw 12 instances when companies had different values according to different fund managers simultaneously.

The markdown by Fidelity on its Snapchat investment follows the buzz in Silicon Valley that unicorns, the term for private companies that have gained value of over $1 billion, such as Snapchat could be on shaky ground. One example of such a trend is the fact that mobile payments company Square has priced itself at about one-third lower compared to its previous value of $6 billion as it seeks to launch an initial public offering.

Snapchat, which features over 100 million daily users, is looking to create more revenue for the company with initiatives such as opening up the platform to advertisers and giving users the ability to replay messages for a fee.

Snapchat also revamped its design earlier in 2015 to attract more users in utilizing the Discover portal, where professional content made for the service can be accessed.