How many end device a XBEE-PRO-S2B coordinator can handle?

I am using XBEE-PRO-S2B module. I am going to associate 48 end devices to a coordinator. But when i associate more than 10 only 10 are forming the network rest are getting disconnected from network and they are not even getting re-associated after reset.Is this because of the child table of coordinator?
Kindly suggest how can i associate maximum end devices without using router to a single coordinator.

Yes that is because an End device is a Child and the Coordinator can only hold 10 end device children in its table. You need to add more Parent Routers to add more Sleeping End Device to your network.