Blackstone Group LP's Harvest Fund Advisors LLC was the biggest institutional buyer among the large investors in the top publicly traded energy pipeline companies during the third quarter, an S&P Global Market Intelligence analysis of SEC filings shows.

The Blackstone unit acquired a combined 40.1 million shares, including 35.2 million units of Williams Cos. Inc. Harvest is Blackstone’s publicly traded MLP and yield-oriented investment platform.

UBS Asset Management Inc. came in second among the big buyers into midstream stocks, with 21 million new shares in the top 10 midstream companies purchased in the third quarter.

Both MPLX LP and Kinder Morgan Inc., as well as ONEOK Inc. and Enbridge Inc., saw more selling than buying from big investors, while Williams saw the most buying during the period, which included a merger with its master limited partnership. Institutions also favored Energy Transfer LP, which completed its own internal consolidation Oct. 19.

None of the top 10 institutional investors most heavily involved in U.S. midstream companies expanded the number of their midstream positions during the third quarter, and only Blackstone saw an increase in the market value of its holdings.