Sri Lanka's power grid crashed on Friday, plunging the entire country into darkness immediately after private companies took over some functions of the state-owned electricity company.
The government ruled out sabotage or action by electrical workers' unions who have threatened blackouts if pay demands are not met, reports Reuters.
The unions have also denied any involvement in the power failure.
State authorities blamed a technical fault in the main line, which left the country without power for more than five hours from early morning.
Kothmale and Kelanitissa are two of the main power stations in the country, responsible for a combined 401MW.