Mapp Biopharmaceutical Inc. is taking new steps to expand production of ZMapp, the experimental Ebola treatment that was provided to several infected patients before supplies ran out in August.

In a statement, the tiny San Diego, Calif., company said it is attempting to improve production yields at its current contract manufacturer, and is also seeking to expand production to an additional facility. In addition, it said it is exploring the use of a different manufacturing method in partnership with an outside pharmaceutical...