A major investor in Ardmore Shipping has added to its strong shareholding in the company.

Russell Investments Group of Seattle has built its stake in the New York-listed tanker owner to almost 10%, an SEC filing shows.

The investor first emerged as a shareholder in Tony Gurnee-fronted Ardmore last year with a 6.17% stake made up of just over two million shares.

A fresh filing shows by the close of 2018 it had amassed a total of 3,112,752 shares in the shipowner.

Based on the present trading price of Ardmore stock at $5.48 each, the Russell stake is worth a shade over $17m.

Donald Smith & Co, Royce and Associates and Aristotle Capital Boston are other major holders of the Ardmore share.

The shipowner has a market capitalization of $188m and a fleet of 27 tankers.