Amid ongoing efforts to contain citrus greening disease, local California officials expanded the quarantine zone this Wednesday.

Officials found infected trees in Corona. The detection comes just a couple of weeks after another quarantine area expansion in the state.

A dozen trees in Riverside County were found with citrus greening. The disease is a devastating threat to the multibillion-dollar California citrus industry, reports the local Press Enterprise.

The CDFA has consequently added 107 square miles to its quarantine area. This now covers the cities of Corona, Norco and parts of Chino.

In total, the quarantine zone encompasses 1,127 square miles across Riverside, San Bernardino, Los Angeles and Orange counties. This past November, the quarantine zone was extended to San Bernardino county.

Such measures restrict the movement of fruit, citrus plants or foliage. However, state officials say that it is safe to consume citrus in the area.

The history of citrus greening in California

Citrus greening infects trees by creating mottled leaves and producing deformed fruit. It eventually leads to the death of the tree.

The presence of the disease began when the industry discovered it in Hacienda Heights in 2012. Since then, the disease has spread across Southern California, impacting 1,741 trees.