Insurance companies in search of yield have increased their exposure to bonds with lower credit ratings and to less liquid securities like non-listed equities and loans, according to a survey by Europe’s insurance watchdog published Thursday.

The survey, looking at investment trends by insurers over the past five years, also found that bond portfolios increased and that big insurers invested increasingly in non-traditional assets like infrastructure, mortgages, loans and real estate.

The Frankfurt-based watchdog, the European Insurance and Occupational Pensions Authority (EIOPA), conducted the survey during the first quarter of 2017. It included responses from 91 insurance companies across 16 countries.

“The survey points to a search-for-yield investment behavior of insurers, which is a natural reaction to the low interest rate environment,” said EIOPA chairman Gabriel Bernardino.

Some 60 percent of respondents said they shifted assets toward more illiquid investments over the past five years, and 58 percent said they had observed a decline in the average investment grade of their portfolios.

EIOPA said the trends “may impact the risk profile” of companies and the sector and “require close monitoring” by supervisors.