Several employees of a pharmaceutical company have been arrested in Indonesia for allegedly washing and reselling used Covid nasal swab test kits.
Up to 9,000 passengers at an airport in Medan may have been tested with the reused swab sticks, say police.
State-owned company Kimia Farma is now reportedly facing a potential lawsuit launched on behalf of the travellers.
Covid nasal swab testing has become routine in many countries hit by the global pandemic.
Police said they believed the scam had been happening since last December at Kualanamu airport in Medan, North Sumatra.
Passengers are required to have a negative test if they want to fly, and the airport offers the option of getting the swabs done on site. Airport authorities had used antigen rapid test kits supplied by Kimia Farma.
Following complaints from passengers that they had received false positive test results, police sent an undercover officer to pose as a passenger last week, reported local news outlet Detik.
When he was swabbed and received a positive test result, other officers swooped in and raided the test site, where they found a used test kit that had been recycled.
Last week, five Kimia Farma employees - including the company's Medan manager - were arrested. The suspects are accused of breaking health and consumer laws by washing nasal swab sticks and repackaging them for sale.
Local media said authorities have compiled reports from 23 witnesses, and are investigating whether the profit from the scam - estimated to be around 1.8bn rupiah (£89,700; $124,800) - was used to fund the construction of a lavish house for one of the suspects.
Kimia Farma, which is headquartered in the capital Jakarta, has since fired the staff involved and promised to tighten internal controls.
This week, two lawyers who frequently flew via Kualanamu airport in recent months, said they were planning to sue Kimia Farma, the South China Morning Post reports.
In a collective lawsuit, they hope to get 1bn rupiah for each passenger who has been affected by the scheme.
Earlier this week, Indonesian authorities said they had identified two cases of the new Covid variant first seen in India.
Last month, Jakarta stopped issuing visas for foreigners who had been in India in the previous 14 days.
The Muslim-majority nation has also banned domestic travel at the end of Ramadan this month, a period which traditionally sees people travelling across the country to visit relatives, and introduced heightened restrictions for other dates.
Indonesia has seen one of the worst Covid outbreaks in Asia, and overall has recorded about 1.7m positive cases and more than 46,000 deaths linked to the pandemic.