A power outage briefly disrupted key railway networks in Tokyo on Tuesday morning, affecting about 41,000 passengers, East Japan Railway. Co. said.

The operator said delays hit a total of 75 trains, including those on the Yamanote and Keihin-Tohoku lines, which run through central Tokyo.

According to JR East, the power outage was caused by an operation error during maintenance work at one of its hub substations in Warabi, Saitama Prefecture.

Services were suspended for up to 40 minutes, with some trains stopped between stations. There were no reports injuries or health problems among passengers, JR East said.