They continued to lie about their program and hid the fact that they were working with South Africa to develop nukes because they had plenty of yellow cake uranium. This continued in 1967 when they did a joint secret nuke test called operation phoenix.

They thought they were being sneaky with the test but failed to account for changing weather patterns in the Indian Ocean. This allowed US spy satellites to pickup the flashes and debris fields. This confirmed that Israel had nukes, but didn't declassify the related documents for decades later.