The club said in a statement: "Our medical staff have confirmed that the Hatters captain suffered cardiac arrest on the pitch, but was responsive by the time he was taken off on the stretcher.
"He received further treatment inside the stadium, for which we once again thank the medical teams from both sides.
"Tom was transferred to hospital, where we can reassure supporters that he is stable and currently undergoing further tests with his family at his bedside.
"We would like to thank everyone for their support, concern and loving messages for Locks."