Q: Will using the same sample group in two publications be considered as salami publication?

Salami publication is broadly defined as a publication practice when data from same study is used in two or more articles. As per the current description of the nature of your data, it seems the second publication can be considered as a salami publication.

Since, we do not have more information on the two publications including the respective research objectives, study designs, data analyses, findings etc., it would not be possible to confirm if this is indeed a case of salami publication.

Generally, presenting the same data/control group in multiple publications is not an ethically acceptable practice. However, in some cases such usage may be acceptable. For example, if the same dataset has been analysed differently in two studies and the objective and conclusion of the two studies are different, the editor of the journal may consider two studies as separate. However, this decision is entirely editorial discretion.

In such cases, the author should inform the editor about the other publication to evaluate the ethical justification of the second manuscript. The authors may need to procure permission from the publishers of the previous study for publishing the second study that uses the same dataset. In the second manuscript, the authors should clearly state which of the results are already published with citation and provide the full source and consent of the original author.

To help the editors and the readers assess the novelty of the study, the author should also clarify what new value the second manuscript is adding to the literature.

Suggested reading:

The importance of avoiding salami slicing in publications: A case study

The pitfalls of "salami slicing": Focus on quality and not quantity of publications

Can two papers with same data but different analysis be considered duplicate publication?

Duplicate publications and simultaneous submissions