How to run multiple simulationClass concurrently?

Hi dear friends,
I have some Simulation Class, each class represent one Transactions related test case. I can run one run:
mvn gatling:execute -Dgatling.simulationClass=scenarios.mySimulationClassSenario

But how can I run multiple simulationClassScenario concurrently?(To add all loads to the system.) Not sequentially…

Thanks,
patric