diff --git a/monai/transforms/utils.py b/monai/transforms/utils.py
index ffbd91690c..23c6bd100a 100644
--- a/monai/transforms/utils.py
+++ b/monai/transforms/utils.py
@@ -344,15 +344,16 @@ def _correct_centers(
         return center_ori
 
     centers = []
+    fg_indices, bg_indices = np.asarray(fg_indices), np.asarray(bg_indices)
+    if fg_indices.size == 0 and bg_indices.size == 0:
+        raise ValueError("No sampling location available.")
 
-    if not len(fg_indices) or not len(bg_indices):
-        if not len(fg_indices) and not len(bg_indices):
-            raise ValueError("No sampling location available.")
+    if fg_indices.size == 0 or bg_indices.size == 0:
         warnings.warn(
             f"N foreground {len(fg_indices)}, N  background {len(bg_indices)},"
             "unable to generate class balanced samples."
         )
-        pos_ratio = 0 if not len(fg_indices) else 1
+        pos_ratio = 0 if fg_indices.size == 0 else 1
 
     for _ in range(num_samples):
         indices_to_use = fg_indices if rand_state.rand() < pos_ratio else bg_indices