The six-line metro rail system will be closed for at least 29 hours from midnight local time Tuesday. US media said an emergency inspection of rail equipment was necessary after a fire caused delays on three lines.
The Washington Metropolitan Area Transit Authority confirmed the closure of the entire subway system for the US capital, at a press conference on Tuesday afternoon.
A spokesman added that safety teams needed to inspect electrical components and power cables on the tracks following a fire earlier in the week.
The subway will shut down at midnight Tuesday and remain closed until at least 5am local time (09:00 UTC) Thursday, which is the regular scheduled opening time. All 91 stations and all six lines will be affected.
Around 600 "jumper cables" will be examined at all tunnel segments in the Metrorail system, a media release from the Authority said.
On Monday, a fire on the tracks at McPherson Square Station led to major delays throughout the system.
The fire was caused by the same kind of electrical component that malfunctioned last year, causing a train to fill with smoke inside a downtown Washington tunnel.
"While the risk to the public is very low, I cannot rule out a potential life-safety issue here," Metro CEO Paul Wiedefeld said. "When I say safety is the highest priority, I mean it. That sometimes means making tough, unpopular decisions, and this is one of those times. I fully recognize the hardship this will cause."
City bus services and shared-ride public transport for the disabled will run normally.
Officials said they expected severe crowding on remaining public transport and advised the public to make alternative travel arrangements.
It will be the first non-weather related shutdown in the subway's 40-year history.
The Metrorail system is the second busiest in the US after New York and serves about 700,000 customers a day in Washington, Maryland and Virginia.
mm/jm (AP, Reuters)