TOKYO, June 1 (Reuters) - Renesas Electronics Corp on Tuesday said restoring full production capacity at a fire-damaged chip plant in Japan would take longer than expected, predicting a return to normal by mid-June rather than the previously estimated end of May.

Capacity on the Naka plant's 300mm chip line in eastern Japan had returned to about 88% of pre-fire levels at the end of May, the company said in a statement. All new equipment would be installed and switched on "by mid-June", it added.

The fire, caused by an electrical fault, was a blow to carmakers around the world already struggling to find enough automotive semiconductors. Renesas makes nearly a third of the microcontroller chips used in cars around the world.

An area of 600 square meters (6,458 square feet) was burned in the fire, with 23 machines destroyed and the ultra-sensitive clean room needed for chip manufacturing filled with smoke and soot.

The Japanese government called on equipment makers to help Renesas, while customers, including Toyota Motor Corp sent officials to help the chipmaker restart the line.

(Reporting by Chang-Ran Kim and Tim Kelly; Editing by Himani Sarkar and Kenneth Maxwell)