The lion, reportedly a 10-year-old male, was chained and did not escape.
The keepers, a man in his 20s, and a female in his 50s, remain conscious but were severely injured.
The two employees were bathing the the lion owned by Shonan Animal Production, a company that rears animals for television productions and film projects.
It made an emergency call at around 11am on January 23, saying the lion kept at the organization in the Japanese city of Narita 'bit' people.Mailonline reports.
Local media reported that the middle-aged woman and a man in his twenties had their face, head and legs bitten when the lion suddenly turned aggressive.
