The government of Ecuador has blamed decades of underinvestment for a nationwide blackout that hit the South American country on Wednesday.

The emergency was reportedly triggered by a failed transmission line, which caused a cascading malfunction and plunged the nation of 18 million into darkness for hours.

Public Works Minister Roberto Luque, who also serves as acting energy minister, said the outage started after 3:00 p.m. local time at the 230,000-volt Milagro-Zhoray connector and spread across the grid. By roughly 6:40 p.m., responders managed to restore coverage to some 95%.

In the intervening hours, power loss caused traffic chaos in large cities, such as Quito and Guayaquil. The capital’s subway system suspended operations. The Education Ministry announced that schools in larger communities would temporarily switch to remote teaching out of concerns for students’ safety.