(CNN) China has revised its official death toll from the novel coronavirus, raising the number of fatalities attributed to the pandemic by more than a third.

Officials in Wuhan, where the virus was first reported late last year, on Friday added 1,290 coronavirus deaths to the city's toll. They also added 325 confirmed cases to the city tally.

The total number of cases recorded in the city now stands at 50,333, with 3,869 deaths. The previous reported death toll for Wuhan was 2,579 -- so the revised figure marks a 50% increase in the number of deaths in the city from coronavirus.

As of April 17, China's National Health Commission had reported 3,342 deaths nationally , before the revised Wuhan figures were published.

Officials explained that the deaths had initially gone uncounted because in the early stages of the pandemic some people died at home, overwhelmed medics were focused on treating cases rather than reporting deaths and due to a delay in collecting figures from various government and private organizations.