The Muslim national, who has been detained for undisclosed reasons, was served processed ham in a meal on the evening of August 3, and has been on a hunger strike since then.
People of Islamic faith are forbidden to eat any kind of meat from pigs.
The man is currently only consuming water and nutritional supplements and immigration officials said his health is not in any danger, the Japan Today reported.
A similar incident occurred in August 2015 where another Muslim man was served a salad with bacon pieces for which the Yokohama area immigration apologised for the “administrative mistake”.
A human rights group safeguarding the rights of foreigners approached the immigration department this week for taking appropriate measures to prevent an occurrence of any other incident of such kind in future.
“The immigration office has the responsibility to provide meals keeping the religious customs in mind, and we request that this doesn’t happen again,” said a representative of the group.
In response the immigration department said, “We regret that this has happened and we are swiftly investigating the cause.”