The deceased have been identified as Ramu (25) and Ravi (28).
Police said the incident occurred at around 4 PM yesterday when the duo, hired by the restaurant on a contract basis, were attending to the clogged septic tank.
Ramu had entered the tank to clean it while Ravi was outside to assist him.
Some time later Ramu collapsed due to suffocation. not getting any response from him, his colleague also entered the tank and he too met the same fate, police said.
Police said the restaurant manager and caretaker have been arrested and a case of culpable homicide not amounting to murder registered against them.