Directors and managers of Phuc Loc Tho, Bao Tin Kim Long, Gofigo, Infobot, Infinity, and Solution Lab were arrested in Binh Thanh District Wednesday for charging usurious interest.
All six companies have offices in Thuy Loi 4 building on Nguyen Xi Street.
The police found documents and electronic data indicating they were lending illegally.
They have licenses to operate as pawnshops and management consultants.
They share the same management and staff and provide loans on websites such as senmo.vn, thantaioi.vn and caydenthan.vn.
Data about 247 transactions the police seized shows the minimum interest rate was 183% annually while the maximum was 2,555%.
The law caps loan interest rates at 20%.
The companies have earned VND442 million ($18,800) from illegal activities, their records show.
The investigation continues.