DETROIT — The city of Detroit found itself in the dark for several hours after a widespread power outage, Tuesday. The blackout affected thousands of people. The cause is still under investigation, but city leaders say Detroit’s aging infrastructure is to blame.

The massive power outage brought downtown to a standstill; it cut power to 1,400 buildings, resulting in people being trapped in elevators and emergency evacuations. Firefighters helped the elderly and disabled.

The power outage plunged schools throughout the Motor City into darkness, including Wayne State University.

Police and fire stations were also in the dark, while prisoners at the main jail were forced into lockdown.

Traffic light outages affected almost the entire city, causing gridlock.

Detroit’s public lighting department said two cable failures are to blame for knocking out the entire grid.

“We’re not certain what happened to the cable; that’s something we’ll have to investigate,” Jerry Norcia, president of DTE Electric, said. “Certainly, I’m sure it’s age-related.”

In financially troubled Detroit, which is emerging from the largest municipal bankruptcy in U.S. history, an aging infrastructure has been a concern for years. Mayor Mike Duggan said the power grid hasn’t been updated in decades and warned that for another few years, there’s still some risk of another such power outage taking place.

The power outage also is a reminder that the older American power grids could be vulnerable to terrorism.

“It’s an ongoing battle to stay one step ahead of these folks who might want to do us some harm, not just physical harm to the power system, but also the cyber side,” said Clark Gellings, of the Electric Power Research Institute.

The positive side in Detroit is that the system that went down only affects public buildings; the rest of the city remained untouched.