diff --git a/ProcessLib/ComponentTransport/CreateComponentTransportProcess.cpp b/ProcessLib/ComponentTransport/CreateComponentTransportProcess.cpp
index 74ce5045f201f31a88622ba82b4e212f1ca7ccd3..8e8741531ac811172dbaf4a2b929065152b4b082 100644
--- a/ProcessLib/ComponentTransport/CreateComponentTransportProcess.cpp
+++ b/ProcessLib/ComponentTransport/CreateComponentTransportProcess.cpp
@@ -53,28 +53,45 @@ std::unique_ptr<Process> createComponentTransportProcess(
 
     std::vector<std::vector<std::reference_wrapper<ProcessVariable>>>
         process_variables;
+
+    // get all process variables stored in a vector before allocation
+    // pressure first, concentration then
+    auto const unalloc_process_variables = findProcessVariables(
+        variables, pv_config,
+        {//! \ogs_file_param_special{prj__processes__process__ComponentTransport__process_variables__pressure}
+         "pressure",
+         //! \ogs_file_param_special{prj__processes__process__ComponentTransport__process_variables__concentration}
+         "concentration"});
+
+    // check number of components for each process variable
+    auto it = std::find_if(
+        unalloc_process_variables.cbegin(), unalloc_process_variables.cend(),
+        [](std::reference_wrapper<ProcessLib::ProcessVariable> const& pv) {
+            return pv.get().getNumberOfComponents() != 1;
+        });
+
+    if (it != unalloc_process_variables.end())
+        OGS_FATAL(
+            "Number of components for process variable \"%s\" should be 1 "
+            "rather than %d.",
+            it->get().getName().c_str(),
+            it->get().getNumberOfComponents());
+
+    // allocated into a two-dimensional vector, depending on what scheme is
+    // adopted
     if (use_monolithic_scheme)  // monolithic scheme.
     {
-        auto per_process_variables = findProcessVariables(
-            variables, pv_config,
-            {
-            //! \ogs_file_param_special{prj__processes__process__ComponentTransport__process_variables__concentration}
-             "concentration",
-             //! \ogs_file_param_special{prj__processes__process__ComponentTransport__process_variables__pressure}
-             "pressure"});
-        process_variables.push_back(std::move(per_process_variables));
+        process_variables.push_back(std::move(unalloc_process_variables));
     }
     else  // staggered scheme.
     {
-        std::array<std::string, 2> variable_names = {
-            {"concentration",
-             "pressure"}};  // double-braces required in C++11 (not in C++14)
+        std::vector<std::reference_wrapper<ProcessLib::ProcessVariable>>
+            per_process_variable;
 
-        for (int i = 0; i < 2; i++)
+        for (auto& pv : unalloc_process_variables)
         {
-            auto per_process_variables =
-                findProcessVariables(variables, pv_config, {variable_names[i]});
-            process_variables.push_back(std::move(per_process_variables));
+            per_process_variable.emplace_back(pv);
+            process_variables.push_back(std::move(per_process_variable));
         }
     }
 
diff --git a/ProcessLib/Utils/ProcessUtils.cpp b/ProcessLib/Utils/ProcessUtils.cpp
index ce4f3f8188a1ee84b4e9fb63f4ec9db634309e37..8e7dfcf2804083af467786e46dce78a3b6288763 100644
--- a/ProcessLib/Utils/ProcessUtils.cpp
+++ b/ProcessLib/Utils/ProcessUtils.cpp
@@ -8,6 +8,7 @@
  */
 
 #include "ProcessUtils.h"
+#include <iterator>
 #include "ProcessLib/ProcessVariable.h"
 
 namespace ProcessLib
@@ -43,17 +44,64 @@ std::vector<std::reference_wrapper<ProcessVariable>> findProcessVariables(
     std::vector<ProcessVariable> const& variables,
     BaseLib::ConfigTree const& pv_config,
     std::initializer_list<std::string>
-        tag_names)
+        tags)
 {
     std::vector<std::reference_wrapper<ProcessVariable>> vars;
-    vars.reserve(tag_names.size());
+    vars.reserve(variables.size());
 
-    for (auto const& tag : tag_names)
+    if (variables.size() > tags.size())
+        DBUG("Found multiple process variables with a same tag.");
+
+    for (auto& tag : tags)
     {
-        vars.emplace_back(findProcessVariable(variables, pv_config, tag));
+        auto vars_per_tag = findProcessVariables(variables, pv_config, tag);
+        vars.insert(vars.end(), vars_per_tag.begin(), vars_per_tag.end());
     }
 
     return vars;
 }
 
+std::vector<std::reference_wrapper<ProcessVariable>> findProcessVariables(
+    std::vector<ProcessVariable> const& variables,
+    BaseLib::ConfigTree const& pv_config,
+    std::string const& tag)
+{
+    std::vector<std::reference_wrapper<ProcessVariable>> vars;
+
+    auto var_names = pv_config.getConfigParameterList<std::string>(tag);
+
+    if (var_names.size() == 0)
+        OGS_FATAL("Config tag <%s> is not found.", tag.c_str());
+
+    // collect variable names to check if there are duplicates
+    std::set<std::string> cached_var_names;
+
+    for (std::string const& var_name : var_names)
+    {
+        auto variable = std::find_if(variables.cbegin(), variables.cend(),
+                                     [&var_name](ProcessVariable const& v) {
+                                         return v.getName() == var_name;
+                                     });
+
+        if (variable == variables.end())
+        {
+            OGS_FATAL(
+                "Could not find process variable '%s' in the provided "
+                "variables "
+                "list for config tag <%s>.",
+                var_name.c_str(), tag.c_str());
+        }
+        DBUG("Found process variable \'%s\' for config tag <%s>.",
+             variable->getName().c_str(), tag.c_str());
+
+        vars.emplace_back(const_cast<ProcessVariable&>(*variable));
+
+        cached_var_names.insert(var_name);
+    }
+
+    if (cached_var_names.size() != var_names.size())
+        OGS_FATAL("Found duplicates with config tag <%s>.", tag.c_str());
+
+    return vars;
+}
 }  // ProcessLib
diff --git a/ProcessLib/Utils/ProcessUtils.h b/ProcessLib/Utils/ProcessUtils.h
index 4c38569e5395f1be33e333475183d57a8f5ad058..11199ccc7e66cc91a602a4ad755d2fa32c8bd724 100644
--- a/ProcessLib/Utils/ProcessUtils.h
+++ b/ProcessLib/Utils/ProcessUtils.h
@@ -40,7 +40,12 @@ std::vector<std::reference_wrapper<ProcessVariable>> findProcessVariables(
     std::vector<ProcessVariable> const& variables,
     BaseLib::ConfigTree const& process_config,
     std::initializer_list<std::string>
-        tag_names);
+        tags);
+
+std::vector<std::reference_wrapper<ProcessVariable>> findProcessVariables(
+    std::vector<ProcessVariable> const& variables,
+    BaseLib::ConfigTree const& pv_config,
+    std::string const& tag);
 
 /// Find a parameter of specific type for a given name.
 ///