SCHENECTADY -- Traffic is expected to be flowing again on State Street through downtown Schenectady starting about 3 p.m. Thursday after a confluence of rain, snow melt and road salt along with an aging infrastructure sparked an underground electrical fire.

Utility crews will likely working well into Thursday evening to repair the damage that forced officials to close the usually busy thoroughfare between Broadway and Clinton Streets in the heart of downtown.

Mayor Gary McCarthy said Thursday afternoon the problems were caused by "water seepage in a vault" that "shorted some secondary lines."

He and Assistant Fire Chief Michael Gillespie said the electric issues below group were more of inconvenience than anything else.

"Other than where it's located, to us, we're not treating it as a major incident," added Gillespie.

There were no injuries of power outages.

For a time, smoke wafted from a manhole cover. A second manhole cover blew off 30 feet into air early Thursday morning, and a city worker who was nearby said it sounded like an explosion.

.@nationalgridus workers trying to diagnose problem. City worker who was nearby when manhole cover flew off said sounded like an explosion pic.twitter.com/s69IHBIQN0 — Emily Masters (@emilysmasters) March 30, 2017

No one is allowed on the street or through businesses' front doors.

State State has been closed since about 4:30 a.m. but buildings have not been evacuated. Fire alarms can be heard in neighboring buildings as smoke enters basements and power surges.

A National Grid spokeswoman said crews are working to determine what is causing the smoke, and no flames have been found. No customers have lost power.

Fire alarms go off in neighboring buildings are smoke gets into basements, power surges. Road will be closed until power is secured. pic.twitter.com/Fh0Y4TlQTF — Emily Masters (@emilysmasters) March 30, 2017

The Broadway intersection remains open.

CDTA said its buses are rerouted to turn right on Erie Boulevard to I-890 to Edison Avenue to Veeder Avenue before returning to their regular routes.