Meanwhile, a growing number of health experts in Italy have been warning of “inconsistencies” with health data released by regional governments during the reopening phase.
Lombardy, by far the worst-hit region, was singled out for criticism, but the region's government angrily denied the claims and threatened to sue.
“There is a reasonable suspicion that the regions are using tricks so they don't have to close again,” Dr. Nino Cartabellotta, head of the Fondazione GIMBE, Italy's group for evidence-based medicine, told Radio 24 on Thursday.
In Lombardy, he said there had been “too many strange things about the data over the past three months”, including people counted as cured when they were released from hospital even when they were still sick.
He said there had also been certain days when few tests were carried out, and delays in the communication of data.
“It's as if there was a kind of necessity to keep diagnosed numbers under a certain level,” Cartabellotta said.
The Lombardy region said the accusations were “very serious, offensive and above all do not correspond to the truth”.
On Friday, Italian newspaper La Stampa said “dozens” of virologists over the past weeks have been “denouncing inconsistencies in the data because it underestimates” the number of infection cases.
And infectious disease expert Luigi Toma told Il Messaggero on Friday there was “something not right about the tracing and monitoring” of the virus, “in Lombardy, but also Piedmont and Liguria”.
The World Health Organization's Italian government adviser Walter Ricciardi said there were “serious reasons to think the data is not reliable in some regions”.
It was “too soon to take a decision” on whether regions could reopen, he told the Repubblica newspaper on Friday, and Lombardy was a particular risk as it still had “20,000 people known to have the virus, as well asymptomatic cases”.
The warning came as Italy's health minister, Roberto Speranza, prepared to evaluate data from the ISS, Italy's Higher Health Institute, on new infections ahead of a final decision on resuming travel to and within Italy in early June.
But Gimbe warned on Thursday that its data analysis showed it was not yet safe to lift travel restrictions on the northern regions of Lombardy, Liguria, and Piedmont, as a further loosening of rules is scheduled for June 3.
From that date, free movement between regions is set to be allowed for the first time in three months, and some foreign travellers will be allowed back into the country.
The government has said it will intervene to keep some regions closed if they are still considered a contagion risk.
Three regions in the south – Campania, Sardinia, and Sicily – have threatened to enforce quarantine on people arriving from northern regions, or to ban them from entering altogether.
According to official figures, more than 33,000 people have died of the virus in Italy – nearly 16,000 of them in Lombardy alone.
The region recorded 382 new cases on Thursday, out of a national total of 593.
Despite being by far the worst-affected region since the beginning of the crisis, Lombardy's government has long been pushing for businesses to reopen as soon as possible.
In an interview with The Local last week, Cartabellotta questioned the accuracy of Italy's regionalized system of testing and data reporting, and accused the Italian government of putting economic interests “ahead of health protection” as it pushed ahead with reopening faster than previously planned.
Nuns walk in a cemetary in Lombardy during the coronavirus crisis. Photo: AFP