Tokyo Station and other Shinkansen stops were packed with people scrambling to buy tickets for other trains.
NHK World's Yamaguchi Hiroaki reports from Tokyo Station.
JR East says the power outage was caused by the failure of an electrical cable above the Shinkansen track in Saitama City near Tokyo at around 10 a.m. Tuesday.
Four bullet trains ground to a halt between stations. More than 350 passengers on a Hokuriku bullet train stranded between Ueno and Omiya stations were evacuated and led to an exit point. A passenger traveling from Kanazawa to Tokyo said he felt relieved to be off the train.
One woman aboard the Hokuriku bullet train says she saw a long pole and an attached part collapse, then heard a loud clunk. She says the window by her seat partially cracked like a spider web.
JR East officials say they have confirmed that metal suspension parts broke at several locations and overhead wiring fell on the Shinkansen line between Ueno and Omiya stations.
Footage taken on the track shows overhead wiring nearly touching the rails.
Officials also say one of the Hokuriku bullet train's pantographs — apparatuses that collect power from an overhead line — was damaged.
JR East sent a crew to the stranded Hokuriku bullet train. An explosion occurred while they were working and smoke rose. Two workers were rushed away in an ambulance. One sustained an electrical shock, while the other suffered burns while brushing sparks off the first worker. Both men remained conscious.
An explosion took place and smoke rose at the site while JR East workers were investigating the power failure, injuring two of them.
The impact of the power failure rippled as train passengers sought alternative modes of transportation. Services soon were fully booked at a bus terminal in Tokyo's Shinjuku area. One man traveling to Nagano by Shinkansen tried but failed to buy a bus ticket there.
JR East says most Shinkansen services resumed on Wednesday. Officials are still investigating the cause of the failure.