Android NDK overflows dalvik JNI local reference table

I have the following problem, from c++ I send huge string[] to java. huge = at most 20 rows; I am doing the following

jint jtype = 2;
jstring emptyString = env->NewStringUTF("");
jobjectArray data = (jobjectArray)env->NewObjectArray(7, env->FindClass("java/lang/String"), emptyString);

env->SetObjectArrayElement( data,0,env->NewStringUTF(item->get_id().c_str());
env->SetObjectArrayElement( data,1,env->NewStringUTF(item->get_number().c_str());
env->SetObjectArrayElement( data,2,env->NewStringUTF(item->get_fullname().c_str());
env->SetObjectArrayElement( data,3,env->NewStringUTF(item->get_mf().c_str());
env->SetObjectArrayElement( data,4,env->NewStringUTF(item->get_dob().c_str());
env->CallVoidMethod(dao, jsaveItem, data, jtype);
int i;
for (i = 0; i < 5; ++i) {
   jstring string = (jstring) env->GetObjectArrayElement(data, i);
   env->DeleteLocalRef(string);
}
env->DeleteLocalRef(emptyString);
env->DeleteLocalRef(data);
env->DeleteLocalRef(dao);

this is happening in a loop so I am doing it for every object I want to save in the database, so as you can imagine, it happends lots of times.

So I am considerate of the VM and delete the local refs of every string I create, but still I get :

 ReferenceTable overflow (max=512)
Last 10 entries in JNI local reference table:
  502: 0x40552880 cls=Ljava/lang/String; (28 bytes)
  503: 0x405528b8 cls=Ljava/lang/String; (28 bytes)
  504: 0x4051f8d0 cls=Ljava/lang/Class; 'Lcom/project/storage/userdata/DataDao;' (212 bytes)
  505: 0x4052eb38 cls=Lcom/project/storage/userdata/DataDao; (12 bytes)
  506: 0x4051f8d0 cls=Ljava/lang/Class; 'Lcom/project/storage/userdata/DataDao;' (212 bytes)
  507: 0x4052eb38 cls=Lcom/project/storage/userdata/DataDao; (12 bytes)
  508: 0x4051f8d0 cls=Ljava/lang/Class; 'Lcom/project/storage/userdata/DataDao;' (212 bytes)
  509: 0x4052eb38 cls=Lcom/project/storage/userda