Only the ringleader, Davide De Vita, was considered sufficiently dangerous to be placed under house arrest, because he continued starting the fires after the others had stopped, police said.
In collusion with the others, De Vita left the base in his car, lit fires or made a false report, then came back to the fire station and waited to be called out to deal with it.
"He demonstrated a sharp criminal ability and had no fear about the consequences of his behavior," the statement said, adding the investigators had recorded the suspects' private conversations.
"On one occasion, De Vita even said he wanted to set off a bomb so as to take the money available if the emergency vehicles needed to be repaired."
The conspirators either used their own telephones to make the false emergency calls, or asked family and friends.
Today, Seville in Spain can expect to see the mercury hit 40C, Rome, Italy, 39C, and Sicily some 42C-44C, but elsewhere, the areas which have experienced extremely high temperatures over the weekend should get a respite.
Athens, Greece is predicted a high of 37 degrees Celsius, Florence, Italy, 35C, and the French island of Corsica - which has been ravaged by wildfire in the past few days - around 34C.
Parts of Macedonia are now in a state of emergency as a result of failure to get wildfires in its southwestern mountainous region under control.
Firefighters and volunteers have been battling wildfires in several regions of Macedonia for about two weeks.
The 30-day state of emergency announced late Saturday by Macedonian Interior minister Oliver Spasovskiby directs all available safety resources will be directed to the affected region.
Police confirmed that a burned body was discovered in a village near the capital, Skopje, while two houses and a barn were burned in the village of Mogilec in Macedonia's central region.
Water-dropping helicopters were requested after fires intensified in the southwest and threatened homes, mostly in mountain villages.
Meanwhile, in authorities in Greece say a wildfire that has blazed on the southern island of Kythira since Friday morning continues to burn unchecked.
So far, no homes have been damaged, but Kythira mayor Efstratios Harhalakis said the fire has consumed at least 3,750 acres of forest and farmland. Four villages and a monastery were evacuated Sunday and a fifth village remained evacuated for a second day.
The Fire Service wouldn't confirm the extent of the damage, but says gusty winds, hilly terrain and highly flammable vegetation make it difficult to control the fire.
The service says 200 firefighters are on the ground and almost all available firefighting planes and helicopters are battling the blaze from the sky.
As of early Sunday evening, more than 40 wildfires had broken out across Greece during the previous 36 hours. Only one remained uncontained.
Italian authorities have reported three deaths linked to violent storms in the wake of the heatwave.
A 41-year-old Belgian man was among the dead after a tree fell on his tent at a Rainbow Gathering counter-cultural summer camp in the Tramontina valley in the northeastern region of Friuli.
Another tree, uprooted by powerful winds, fell on a festival at Marzia in the Dolomites, killing another man.
A hiker was fatally struck by lightening on a path up a mountain in the same area, the Marmolada.
The weather-related deaths follow a storm-triggered mudslide on Saturday which swept a woman to her death on the outskirts of the ski resort of Cortina d'Ampezzo.
Rainfall in July was nearly 50 percent lower across Italy than is normal and peak temperatures have been hitting at least 40C across nearly the entire country for almost a week.
The highs are not unusual but the duration and widespread nature of the heatwave is, weather experts say.
