NEW DELHI (CNN)Thousands of people have fallen prey to an elaborate wide-ranging scam selling fake coronavirus vaccines in India, with doctors and medical workers among those arrested for their involvement, authorities say.

At least 12 fake vaccination drives were held in or near the financial hub Mumbai, in the country’s western Maharashtra state, said Vishal Thakur, a senior official of the Mumbai police department.

“They were using saline water and injecting it,” Thakur said. “Every fake vaccination camp that they held, they were doing this.”

An estimated 2,500 people were given fake shots, he said. The organizers charged their victims fees for the shots, earning up to $28,000 in total.

“We have arrested doctors,” he added. “They were using a hospital which was producing the fake certificates, vials, syringes.”

So far, 14 people have been arrested on suspicion of cheating, attempts at culpable homicide, criminal conspiracy, and other charges. More arrests may come as police continue investigating other people involved in the scam, Thakur said.

India was ravaged by a second wave of coronavirus between April and early June, which infected millions and killed tens of thousands nationwide. After peaking in May, daily cases have slowly declined, easing the pressure on the strained medical system — and allowing authorities to step up their vaccination program during the country’s recovery.