QUITO, Dec. 14 (Xinhua) -- At least four people were killed and another 20 injured in a traffic accident in the town of Conocoto, southeast of the Ecuadorian capital of Quito, the ECU-911 Integrated Emergency Services System reported Friday.

The accident was reported at 7:17 a.m. local time through a telephone call to the 911 emergency hotline, the agency said in a statement.

According to the ECU-911, a bus overturned on Princesa Toa Avenue, which connects Conocoto to southern Quito.

"As a result of the accident, four people died and 20 were injured, who were attended by rescue personnel," the agency said.

The bus was carrying about 50 passengers and before overturning, it crashed into other vehicles and struck the wall of a residential complex and two electricity poles, according to local media reports.

The traffic authorities have not released the cause of the accident, however a failure in the brake system of the bus is suspected.