The Dutch player, who was handed a warning and suspended following his previous remarks about the war, was cleared to return to training on Monday after showing remorse, the club said in a statement at the time.
El Ghazi, however, posted another statement on Wednesday that the club said was 'incomprehensible' and would now examine it from a legal perspective.
"For the avoidance of doubt, my statement on 27 October 2023 was my only and final statement both to FSV Mainz 05 and the public relating to the social media posts made by me over the last few weeks," El Ghazi wrote.
"Any other statement, comments or apologies to the contrary attributed to me are not factually correct and have not been made or authorised by me. My position remains the same as it was when this started.
"I am against war and violence. I am against the killing of all innocent civilians. I am against all forms of discrimination. I am against Islamophobia. I am against anti-Semitism. I am against genocide. I am against apartheid. I am against occupation. I am against oppression."
He said he had "no regrets or remorse" regarding his position and refused to distance himself from what he had previously said.
El Ghazi, who joined Mainz in September and also played for Aston Villa and Everton in the Premier League, had been suspended on October 17th over the post which he has since deleted.
On Wednesday, however, he wrote: "I do not owe special responsibility to any state. I do not believe any people or states are beyond question and accountability, nor are they above international law."
"There can never be any justification for the killing of over 3,500 children in Gaza in the last three weeks... I and we as a world cannot conscionably (sic) remain silent. We must call for an end to the killing in Gaza now."
The Hamas attack on southern Israel on October 7th that triggered the hostilities killed about 300 soldiers and 1,100 civilians, Israel says.
The Gaza health ministry says at least 8,796 Palestinians, including 3,648 children, have been killed in Israeli strikes on Gaza since then.
Mainz said on social media on Wednesday they had read his latest statement in relation to the club "which we noted with surprise and incomprehension".
"The club will check the issue legally and then evaluate it. The player registered sick on Monday and is currently not part of the training activity."
Mainz, without a league win this season, are in last place in the Bundesliga with three points and play RB Leizpig on Saturday.
