About 40 people were injured in the attack, of whom 29 remain in hospital, seven in critical condition. Four people, including the attacker, died.
"She has signed the book of condolence and she has recently returned to Number 10 (official residence) after a private visit to a hospital where she spent around 40 minutes speaking with victims of yesterday's events, ward staff, clinical staff ... to thank them for their work," the spokesman told reporters.
May also met Queen Elizabeth on Wednesday evening for a regular meeting, he said.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)