Authorities have detained 88 people for suspected involvement in an investment scam targeting retirees, the public security department of Beijing’s Haidian district said Tuesday.

The detained people are suspected of “illegal fundraising” in connection with Zhongan Minsheng Elderly Service Co. Ltd, a company that promoted itself to elderly customers as a “reverse mortgage” provider.

Caixin reported Monday that the company had asked retirees to pledge their Beijing homes to borrow money for investment in Zhongan-managed projects, in exchange for attractive returns. But instead of receiving the promised returns, customers soon found themselves hounded by debt collectors, as Zhongan had put their names on the company's deals with other entities. The business model marketed by Zhongan doesn’t appear to be in line with the reverse mortgage concept approved by the government, an industry expert told Caixin.

The public security department said in its Tuesday statement that those involved in the scheme must voluntarily surrender and return any illegal gains. An investigation into Zhongan is ongoing.

Related: In Depth: ‘Reverse Mortgage’ Trap for Retirees