SAN GIORGIO IONICO, Italy — Her husband can still recall how Paola Clemente used to set two alarms to make sure she woke in the middle of the night — 1:50 a.m. — to catch the private bus that would take her and dozens of other women to the vineyards.

There, she would pick and sort table grapes up to 12 hours, taking home as little as 27 euros a day, about $29, after middlemen skimmed her pay. Sometimes she was so exhausted, she fell asleep in the midst of conversation.

Her death of a heart attack at 49 in the fields has set off nearly two years of soul-searching in Italy over what the authorities, labor experts and union organizers described as an elaborate system of modern-day slavery — involving more than 40,000 Italian women, as well as migrant and seasonal laborers — that remains at the core of Italy’s agricultural economy, especially here at the country’s jagged heel.

After months of investigation, this year the authorities arrested six people, accusing them of using their recruiting and transportation agencies to extort wages from women so poor and desperate they dared not speak up and worked under extreme conditions.