Southwest Water Co. said that its stockholders have approved the company’s $427 million acquisition by a group of institutional investors.

The Los Angeles water utility company in March agreed to be taken private for $275 million in cash, or $11 per share, plus assumption of debt. The acquiring group is a partnership between Water Asset Management LLC and J.P. Morgan Asset Management, both of which are making the investment on behalf of their institutional investors.

The new owners plan additional investments to upgrade the company’s water service infrastructure.

The company late Friday said it has received regulatory approval from Oklahoma for the proposed merger. California is the sole remaining state from which approval is needed.

Shares were down 2 cents, or less than a percent, to $10.93 in midday trading on the Nasdaq.