The Pozzo family, who purchased Watford in 2012, are understood to be one of three potential investors looking to buy the club, according to A Bola.
Tondela are an attractive proposition after earning promotion from the Portuguese second division two seasons ago and establishing themselves last term by finishing 16th.
The team, coached by Gilberto Coimbra, are currently 15th in the table and, more importantly for the investors, completely debt-free.
Giampaolo Pozzo, who also owns Udinese and handed over Watford to his son in the last few years, has vast experience of running clubs, having also previously helmed Granada before selling to a Chinese group.
Former Barcelona and Chelsea star Deco, who works for agent Jorge Mendes, and a Chinese investor are the other contenders reportedly vying for control of Tondela.