Smoke filled Ginza Station in Tokyo on Tuesday morning, briefly disrupting Hibiya Line operations, police and the subway operator confirmed.
The police were alerted at around 6:55 a.m. after smoke was seen pouring out of a ceiling duct inside the underground station.
No injuries were reported, though many passengers covered their mouths with handkerchiefs as they hurried toward the ticket gates, NHK reported.
Tokyo Metro Co. said the smoke was coming from garbage in the ventilation system.
Firefighters extinguished the fire and began investigating how it started.
Tokyo Metro temporarily suspended operations on the entire Hibiya Line, affecting about 68,000 commuters.