One filing dated May 31 showed funds including Fidelity's well-known Contrafund holding stakes in companies like Facebook, game maker Zynga Inc and coupon provider Groupon Inc, for instance.
Funds run by other big asset managers including T. Rowe Price have also purchased stakes in the privately held companies, which do not disclose many financial details. Fidelity of Boston had previously declined to discuss its interest in social-media shares.
Fidelity spokesman Vin Loporchio said more than 30 of the company's funds held shares of Facebook as of the end of April. The investments represented no more than 0.15 percent of any individual fund's total assets, however.