Downtown Los Angeles investment firm Oaktree Capital is acquiring Highstar Capital, a New York firm that invests in physical infrastructure for the energy industry, Oaktree announced Monday.

Highstar’s investments include a stake in Caiman Energy of Dallas, a servicer of natural gas producers.

The deal is expected to close in the third quarter, when Oaktree will become manager of the $2.3 billion Highstar Fund IV. Terms of the deal were not disclosed.

Oaktree Managing Director Ian Schapiro said the acquisition is a natural extension of Oaktree’s existing energy investment strategy, and will open up further opportunities.

“We believe the time is right to capitalize on our extensive experience in this market and our access to proprietary deal flow by investing directly in infrastructure opportunities,” Schapiro said in a statement.

The acquisition complements Oaktree’s power opportunities fund, which invests in middle market energy and power companies.