"The disintegration happened in the air and the fragments are strewn over a large area," committee chief Viktor Sorochenko was quoted as saying by RIA-Novosti news agency in Cairo, where he is part of an international panel of experts from Russia, Egypt, France and Ireland.
Sorochenko said it was "too early to draw conclusions" about what caused the crash yesterday, which killed all 224 people travelling from Egypt's resort Sharm el-Sheikh to Saint-Petersburg.
The Interstate Aviation Committee (MAK) is Russia's top body for investigating air accidents. Sorochenko was appointed yesterday to head a panel of crash experts to Egypt.
Investigators have recovered the plane's "black box" flight recorder and the Egyptian government said today its contents were being analysed.