SACRAMENTO, Calif.—The nation's largest teacher pension fund is taking the first step toward divesting from companies that manufacture guns and high-capacity magazines that are illegal in California.

The investment committee of the California State Teachers' Retirement System unanimously approved a motion by state Treasurer Bill Lockyer on Wednesday.

CalSTRS is invested in private equity firm Cerberus Capital Management, which owns the manufacturer of an assault rifle used in last month's Connecticut school massacre. The pension fund also owns shares of Sturm, Ruger & Co. and Smith & Wesson Holding Corp., two publicly traded gun manufacturers.

Those investments account for $11.7 million of the system's $155 billion portfolio.

Board member Harry Keiley says the fund has the power to change its investments. Staff will meet with the companies and return with recommendations.