SANA’A, March. 7— Darkness returned to Sana’a and other governorates after unknown persons bombed power lines in Marib governorate on Wednesday, said representatives of Yemen’s Public Electricity Corporation.

Khaled Rashed, head of the corporation, told the Yemen Times that a team has thus far been unable to repair the lines, as it has been unable to determine where the attack occurred.

Power supply lines have remained vulnerable to sabotage by armed tribesman over  the past months. During these months, power outages have lasted up to 20 hours a day.

Over the last few weeks, electricity output has greatly improved, allowing Yemenis to feel optimistic an improvement that came in conjunction with the holding of the early presidential election.

In recent days, sheikhs from Marib have agreed to protect power lines. They vowed to kill anyone acting against the public interest.