By Phoebe Sweet

Published Tuesday, March 25, 2008 | 3:46 p.m.

Updated Thursday, Oct. 30, 2008 | 2:14 p.m.

Turns out environmentalists aren’t the only ones interested in the money behind Sierra Pacific Resources, the company that owns Nevada Power Co. and Sierra Pacific Power Co.

The Federal Energy Regulatory Commission’s Office of Energy Market Regulation has requested more information on the relationship between Sierra Pacific and its largest investor, Wall Street firm Horizon Asset Management.

Environmentalists raised questions in January about why Horizon had not come to the Nevada Public Utilities Commission for approval of its purchase of more than 25 percent of Sierra Pacific, as required in Nevada. They were also concerned that the company has a history of investing in troubled utilities, and of foisting risk onto consumers rather than shareholders.

Now it appears Horizon may have been skirting federal as well as state regulations when purchasing more than $756 million worth of Sierra Pacific stock. Horizon is required to get FERC approval before purchasing more than $10 million of any utility company.

According to FERC, Horizon also owns more than $10 million of Allegheny Energy, CenterPoint Energy, CMS Energy Corp., Mirant Corp., NRG Energy and Reliant Energy. Horizon also is a 6.5 percent owner of Dynegy/LS Power, which proposed a 1,590-megawatt coal-fired plant outside Ely, near a Sierra Pacific Resources proposed plant.

In a March 25 letter to Horizon’s chief compliance officer, Andrew M. Fishman, and to law firm Drinker Biddle and Reath, FERC says it learned of the issue from media reports.

Read the last blog on Horizon.