MANILA, Philippines — The National Grid Corporation of the Philippines (NGCP) issued a Yellow Alert for the Luzon grid on Wednesday because of leaks in the boiler tubes of some plants.

According to the transmission firm, the yellow alerts are up from 2 p.m. to 4 p.m., and 5 p.m. to 10 p.m.

A yellow alert is issued when the operating margin is insufficient to meet the transmission grid's contingency requirement.

According to the NGCP, the reason for the interruptions were boiler tube leaks from two main power plants, causing one to trip and the other to operate at lower capacity.

Meanwhile, the NGCP said operations in the Visayas and Mindanao grids were normal.