A New York City councilman is calling for a hearing to look at nonprofit city contractors after officials opened an investigation into the allegedly undisclosed business ties that a top homeless shelter provider has with a security firm.

The Wall Street Journal reported Thursday that the city’s Department of Investigation had opened a probe into the relationship between Acacia Network Housing Inc., a nonprofit homeless services provider, and SERA Security Services LLC. SERA was founded by the Acacia’s CEO, Raul Russi.

Since 2010, Acacia has received more than $1 billion in contracts from the city’s Department of Homeless Services to operate shelters. The nonprofit paid more than $12 million to SERA in 2017 for the firm to provide security services at some of Acacia’s shelters, according to the nonprofit’s most recent federal tax filing.