According to a Japanese newspaper, Osaka citizens noticed a whale about 8 meters in length which had entered the Yodogawa river.
"Whales have never swum into our river before. It was probably here by accident, chasing prey," the newspaper quoted a local oceanarium employee, who called the appearance of the giant mammal "an exceptional event."
A Japanese TV channel shared a video of the whale swimming in the river, and it quickly went viral.
The Japan Coast Guard was notified about the whale near Osaka Bay at around 8 a.m.
Officers from 5th Regional Coast Guard Headquarters are currently monitoring the animal's behavior from a patrol boat, gathering information on its health status. They are also alerting nearby ships about the whale's movements.