Sierra Pacific Industries (SPI) is to close two sawmills in California this summer.

The Camino mill will run until June 12, while the Sonora sawmill and a related biomass power plant will close in mid-July.

The move, which involves laying off 310 workers, follows the company’s announcement earlier this month that it will close its small-log sawmill in Quincy, California on May 4, affecting around 150 employees.

The company said the closures were due to extremely low lumber prices and a costly and difficult regulatory environment, the Sacramento Business Journal reports.

A reduction in harvested timber was also a factor.

SPI said there were no plans to liquidate the plants and shifts could be resumed when the market strengthens.