How to search for all Units that belong to Unit Group?

I am using the Wialon Hosting Javascript API and I can't seem to find a quick way to do the following:

I need to retrieve all the units (as well as their last message and position fields) that belong to a certain group. This seems like a simple task but I can't figure out a direct way to do it. When doing a search for avl_unit_groups, I can get a list of unit ID's belonging to a specific group. However, the only way to get last message and position data about these units is to do a search by itemID for each unit. This method seems inefficient and I am hoping there is a better way.

What is the best way to get all the Units in a specific unit group as well as their last message and position fields? (not just their Unit ID's)

Any insight would be greatly appreciated. Thanks in advance!