The East Japan Railway Company says all services on two major lines in Tokyo are suspended due toa power outage. The Yamanote Line and the Keihin-Tohoku Line, two of the city’s busiest routes, have been affected since Friday morning.

Some stations across the Tokyo area are seeing major congestion and crowding. Rail officials are also restricting passengers from entering in some areas, in order to limit the number of people inside.

The outage has caused a major transit disruption for passengers in one of the world’s largest cities, one known for its reliable train network. The East Japan Railway Company says the power outage started around 4 a.m. after a substation tried to send electricity to overhead wiring. The Keihin-Tohoku Line resumed operations around 7 a.m., but had to suspend its services again later.

The company says it expects all services to come back online around 1 p.m. local time.