The IRS said it caught scammers who stole more than $1.8 billion from federal COVID-19 relief funds intended to help small businesses and workers affected by the pandemic.

The massive amount of theft was uncovered over two years by IRS criminal investigations into more than 660 tax and money-laundering cases involving stimulus funds doled out as loans, credits and payments, the IRS said Wednesday.

The total amount stolen from the federal government’s $2 trillion in pandemic aid may be many times higher. Back in December, the U.S. Secret Service estimated that at least $100 billion had been stolen from COVID-19 relief programs, mostly from unemployment fraud. That figure did not include cases like those uncovered by the IRS and prosecuted by the Justice Department.

“Unfortunately, even during times of crisis, criminals pop their heads out to look for ways to take advantage of those in their most vulnerable state,” Jim Lee, chief of IRS criminal investigations, said in a statement.

The IRS said it has had a 100% conviction rate for scammers who have been prosecuted, with prison sentences averaging 42 months.

The fraud involved money appropriated by the Coronavirus Aid, Relief and Economic Security Act, or CARES, signed into law two years ago in response to the pandemic. The measure authorized more than $2 trillion in aid.

Many of those the IRS caught scamming submitted fraudulent Paycheck Protection Program loan applications that cited fake businesses and employees. Some were accused of using the taxpayer money for lavish spending sprees, purchasing luxuries like Lamborghinis, Rolex watches, designer handbags and houses. After coming under suspicion, others attempted to fake their own death or flee the country.

The Justice Department’s criminal division last month reported recovering more than $75 million in cash plundered from PPP funds, as well as real estate and luxury items purchased with fraudulent proceeds. The valuables were seized in cases involving more than 150 defendants in 95 criminal cases.