The tourists and four Egyptians were killed by security forces on September 13, 2015 when they came under fire during a lunch break in Egypt's vast Western Desert while on their way to the Bahariya oasis.
Survivors have told Mexican diplomats that came they under fire from a plane and helicopters.
Egypt said the tourists had entered a restricted area and were "mistakenly" killed as security forces chased jihadists.
"The families of three of the victims have each received a bank transfer worth USD 140,000," said Ahmed Ibrahim, treasurer of the Egyptian Travel Agents Association.
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Their lawyers signed the agreement last week, he said.
"Negotiations are under way with the other five families in order to close the case definitively," Ibrahim said.
Egyptian foreign ministry spokesman Ahmed Abu Zeid confirmed that an agreement had been reached to compensate three of the eight families.
He said the accord was between the federation and the families and that the Cairo government was not involved.
Ibrahim said the federation agreed to compensate the families after an investigation found that the travel agency looking after the tourists was responsible for their deaths.