Rex Heuermann, a former New York architect charged with killing four sex workers whose remains were found on a Long Island beach more than a decade ago, will face additional charges related to multiple other victims, a source with direct knowledge of the matter told NBC News.

Heuermann, 60, is expected to be arraigned Thursday morning, the source said.

The indictment remains sealed, the source said, and additional details were not immediately available. The new charges are expected after investigators returned last month to search Heuermann’s home in the suburban Long Island community of Massapequa Park.

An area in Manorville, roughly 40 miles from Heuermann’s home, was also searched.

Heuermann was arrested in July and charged with murder in the killings of Melissa Barthelemy, 24; Megan Waterman, 22; and Amber Lynn Costello, 27. He was charged earlier this year in the killing of Maureen Brainard-Barnes, 25.

The women disappeared between 2007 and 2010. Their remains were found in December 2010 around Gilgo Beach, on Long Island’s south shore. Authorities made the discoveries while searching for Shannan Gilbert, a sex worker who disappeared from the nearby gated community of Oak Beach.

Gilbert, 23, was last seen running from a client’s home on May 1, 2010. Her remains were found in a marsh in December 2011. Authorities have said they believe she may have drowned, but an autopsy performed by revered forensic pathologist Michael Baden said she had been the victim of violence, possibly strangulation, without concluding how she died.

The remains of several other people were discovered during the Gilgo Beach search, including those of Jessica Taylor and Valerie Mack. Partial remains of Taylor and Mack, both sex workers, were also found in Manorville, roughly 45 miles east of Gilgo Beach.

Heuermann, who is being held without bail, has maintained his innocence in the killings of the four women. He has not been charged in the deaths of Taylor or Mack.

Authorities connected Heuermann to the earlier cases in part through strands of his estranged wife’s hair, which was obtained from burlap sacks in which the remains were found. Charging documents say that Heuermann’s former partner and children were traveling out of state when he is alleged to have killed the women.

This article was originally published on NBCNews.com