Hidden cameras and intercepted phonecalls recorded thousands of instances of absenteeism at the Loreto Mare in the southern city. The investigation took two years in total.
While staff skipped work, two medical social workers were seen clocking in on behalf of around 20 colleagues each day, using their ID.
"One doctor who was recorded as present had left in a taxi to play tennis, carry out private errands and go jewellery shopping," said police.
"And one employee who was in charge of supervising staff left during office hours to work as a chef at a hotel in Nola."
In total, 55 people - including doctors, nurses, radiographers, social workers and administrative staff - were placed under house arrest on Friday morning, at the request of the public prosecutor.
Fifty of them however have been authorized to leave their homes in order to go to the hospital for work.
The absenteeism phenomenon
The problem of time clock dodgers hit the front pages in October 2015 after 35 people were arrested in San Remo in northwest Italy and 195 people were placed under investigation for absenteeism.
Numerous stories of absenteeism have made headlines in Italy ever since, while the government has vowed to crack down on the phenomenon.
Last year, the Italian cabinet passed a law making it easier to sack work-shy public sector staff, leading Prime Minister Matteo Renzi to declare that the “good times were over” for time clock cheats.
Employers who choose to turn a blind eye to the time-stamp swindlers risk disciplinary action too under the new laws.
But the problem was not to be solved so easily, as proved by the case of some determined time cheats in southern Italy, who grew wise to the hidden cameras and wore cardboard boxes over their heads to evade identification.