The scandal first erupted last month when the customs administration said that an agent within President Tsai Ing-wen's entourage tried to bring in 9,800 cigarette cartons as he returned from an official trip accompanying the island's leader to the Caribbean.
The agent pre-ordered the cigarettes online in Taiwan, stored them at an airport warehouse, and then planned to smuggle them past customs onto government vehicles as Tsai's motorcade left, authorities said.
It soon emerged that the scam was far from a one-off after China Airlines released figures showing huge amounts of duty-free cigarettes were routinely ordered during presidential visits, both for Tsai and her predecessor Ma Ying-jeou's trips abroad.
Tsai has said she had no idea her security team was involved in the scam and has ordered investigations.
On Friday, the head of the secretive National Security Bureau took the rare step of holding a press conference, which revealed 76 people involved in presidential security have been implicated so far -- including 25 agents, as well as Tsai's bodyguards and military police.
"I promise that the investigation will not end until the whole case is clarified," said Chiu Kuo-cheng, whose predecessor resigned last month when the scandal was exposed.
He added his investigation would pursue any military rank and that he would be "heavy-handed" in his response.
Investigation details released by the NSB suggest most agents only bought a few dozen cartons of cigarettes -- the majority ordering between 11 and 50 cartons.
The largest purchase uncovered so far was a major who bought more than 1,000 cartons -- and the highest rank implicated is a major-general.
The scandal comes as Tsai seeks a second term in a January presidential election against Kaohsiung mayor Han Kuo-yu of the Beijing-friendly Kuomintang party.
Taiwan's customs law limits travellers to a maximum five cartons of cigarettes -- and only one can be tax-free.
So far two agents have been detained for their alleged involvement in the case, while prosecutors also questioned several airline officials responsible for ordering duty-free products.