DUBLIN, Ga. (AP) _ Southeast Paper Manufacturing Co. has officially announced a $300 million expansion of its Laurens County newsprint plant.

The expansion, which had been expected, became official with the approval of the boards of directors of Southeast's three owners: Cox Enterprises Inc., Knight-Ridder Inc. and Media General Inc.

The project will more than double the production capacity of the plant, which uses recycled newspapers to turn out more than 210,000 tons of newsprint annually.

It will mean as many as 130 new permanent jobs and a construction payroll of up to $30 million, said Southeast Paper President and General Manager Ron Wilson. He said construction will begin this fall and should be completed by late summer 1989.

CRS Sirrine Co. of Greenville, S.C., will be the design engineering firm and BE&K of Birmingham, Ala., will be the construction manager and general contractor. Both companies were involved in the initial construction of the Laurens County plant, which began operating in June 1979.