diff --git a/flaml/automl.py b/flaml/automl.py
index 71d7bd43b6..34172bfab1 100644
--- a/flaml/automl.py
+++ b/flaml/automl.py
@@ -1026,12 +1026,25 @@ def _validate_ts_data(
             assert (
                 dataframe[[dataframe.columns[0]]].duplicated() is None
             ), "Duplicate timestamp values with different values for other columns."
-        ts_series = pd.to_datetime(dataframe[dataframe.columns[0]])
-        inferred_freq = pd.infer_freq(ts_series)
-        if inferred_freq is None:
-            logger.warning(
-                "Missing timestamps detected. To avoid error with estimators, set estimator list to ['prophet']. "
-            )
+        if self._state.task == TS_FORECASTPANEL:
+            # check for each time series independently
+            group_ids = self._state.fit_kwargs.get("group_ids")
+            group_df = dataframe.groupby(group_ids)
+            for group in group_df:
+                ts = group[1]
+                ts_series = pd.to_datetime(ts[ts.columns[0]])
+                inferred_freq = pd.infer_freq(ts_series)
+                if inferred_freq is None:
+                    logger.warning(
+                        "Missing timestamps detected."
+                    )
+        else:
+            ts_series = pd.to_datetime(dataframe[dataframe.columns[0]])
+            inferred_freq = pd.infer_freq(ts_series)
+            if inferred_freq is None:
+                logger.warning(
+                    "Missing timestamps detected. To avoid error with estimators, set estimator list to ['prophet']. "
+                )
         if y_train_all is not None:
             return dataframe.iloc[:, :-1], dataframe.iloc[:, -1]
         return dataframe