Native American children have attended at least 523 Indigenous boarding schools since the 19th century, including hundreds that were run by the federal government to assimilate children into White society, a non-profit group says.

The National Native American Boarding School Healing Coalition released a new list of Indigenous boarding schools Wednesday that surpasses the number of previously reported institutions.

The list of Indigenous boarding schools in the United States includes many that have closed and some that are still in operation today.

Last year, the Department of Interior released a review of the past efforts by the federal government to assimilate Native American children into White American society. It found the federal government ran or supported 408 boarding schools that forced assimilation between 1819 and 1969.

Deborah Parker, the coalition’s CEO, told CNN that her group identified an additional 115 institutions, the majority of which were operated without federal support.

“There’s just so much we don’t know and trying to get records from churches has been incredibly difficult until now. We’re starting to get some records, but it’s just not enough,” Parker said. “We’re really trying to build this movement so that we can help families find their loved ones.”

Parker said people in many Indigenous communities are still looking for relatives who were taken to boarding schools.

“They’re still trying to search for information that could lead them to where their family members are. We know that many, many children died in the boarding schools and yet, we don’t know where they’re right now,” Parker said.

The coalition’s list includes institutions that meet three requirements: the institutions must have been designed specifically for Native American children, have an educational component and house students for any period of time. The Interior Department had similar criteria but only counted schools opened before 1969 that were operated or directly supported by the US federal government.

The list also includes 125 schools that are currently open and that were or are considered Indigenous boarding schools.

Throughout the 19th and 20th centuries, Native American children were sent to schools where they were renamed, told not to use Indigenous languages and had their hair cut, the Interior Department’s review states.

Hundreds of those schools were operated or directly supported by the US government but many were also run by religious groups and churches after Congress passed the Civilization Fund Act in 1819. The legislation provided religious organizations with the resources to run more than a hundred schools for Native American children. Many operated like military training camps where children were subject to abuse, neglect and corporal punishment.

In recent years, efforts to raise awareness about the legacy of boarding schools have gained momentum with Interior Secretary Deb Haaland – the nation’s first Native American to serve as cabinet secretary – who launched an initiative to investigate the boarding schools.

The Interior Department’s initial investigation found that 19 boarding schools accounted for the deaths of more than 500 American Indian, Alaska Native, and Native Hawaiian children but noted the number of recorded deaths was expected to rise, CNN previously reported.

“The Department expects that continued investigation will reveal the approximate number of Indian children who died at Federal Indian boarding schools to be in the thousands or tens of thousands,” the report said.