XA datasources memory leak

I'm experiencing problems with XA datasources on jboss 7 and postgres database. The test application periodically (each 5 seconds) performs several JPA queries. I use @Schedule facility on @Singleton @Startup bean. However, after a few days, the server runs out of memory. Switching to local tx datasources seems to fix the problem. Analysis of heap dump using visualvm gives the following:

Heap is quite full (~490 MB from 512MB), most space is taken by byte[] (40%, 200MB) and HashMap.Entry (16%, 80MB) objects, so that gives no much information. Computing retained sizes shows that most space (but just ~16MB) is taken by com.arjuna.ats.internal.jta.recovery.arjunacore.XARecoveryModule#1. Further analysis shows that XARecoveryModule._xidScans contains ~8000 entries. The size continuously grows. When the dump is taken before the OOM conditions starts, eg. when the heap is 50% full, the size of this hashmap is ~4000, so it looks like it grows continuously.

I will attach my example test case.