mpiexec error on HPC: execvp error on file srun (No such file or directory)

Question

On the HPC, I first test

apptainer exec my_container bash -c "activate environment; python3 script.py"

It worked well.

Then it also works well if I use terminal interactively like:

apptainer shell my_container
activate environment
mpiexec -n 5 python3 script.py

But, if I tried to write a slurm script with

apptainer exec my_container bash -c "activate environment;mpiexec -n 5 python3 script.py"

I got the following message: [mpiexec@acn89] HYDU_create_process (lib/utils/launch.c:73): execvp error on file srun (No such file or directory)

Any helps are greatly appreciated.