I think the media tends to just copy other media's stories (that is how it seems in other cases I follow), so I wouldn't put a lot of weight in that unless it says it heard a direct quote from someone who actually said/reported about the change before/after takeoff.
If we go to 'the horse's mouth', which is French newspaper 'Le Parisien', it says:
"Un rapport sur les passagers et les bagages emmenés à bord vient d'être remis aux juges d'instruction. Son auteur était présent au tribunal lors de la réunion. « On se rend compte qu'il y a plusieurs listes de passagers contradictoires, par exemple sur le placement des passagers, indique Ghyslain Wattrelos. On a aussi appris qu'un mystérieux chargement de 89 kg avait été rajouté sur la liste du vol après son décollage. Un conteneur était également surchargé, sans qu'on sache pourquoi. L'expert n'en tire aucune conclusion. C'est peut-être de l'incompétence ou une manipulation. Tout est possible. Ça fera partie des questions à poser aux Malaisiens. »"
which, according to google-translate, says this in English:
"A report on the passengers and baggage brought on board has just been given to the investigating judges. Its author was present in court at the meeting. "We realize that there are several contradictory passenger lists, for example on the placement of passengers, says Ghyslain Wattrelos. It was also learned that a mysterious load of 89 kg had been added to the flight list after take-off. A container was also overloaded, without anyone knowing why. The expert draws no conclusion. It may be incompetence or manipulation. Everything is possible. This will be part of the questions for Malaysians. ""
Vol MH370 : révélations sur le crash mystère
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The first link (msn) seems to be saying that the additional 'item' weighing 89kgs was added to the plane before takeoff, but not added to the 'list' until after takeoff.
"French investigators searching for answers over the disappearance of flight MH370 have discovered a 89kg weight was added to the flight before take-off, it has been reported.
....
Two Parisian judges are currently conducting a judicial investigation, and have just received a report on the passengers and baggage brought on board, French newspaper Le Parisien reported.
According to the paper, Mr Wattrelos said: “It was also learned that a mysterious load of 89 kg had been added to the flight list after take-off."
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So is this to mean that a last minute 'item' weighing 89Kgs was added to the plane, but not recorded until 'after' takeoff? (And if added 'after' takeoff, where are these people finding this list?? Is it a computerized list they would have access to even though the plane is missing??)