PROVIDENCE, R.I. — Volunteers who conducted the most extensive survey of Rhode Island’s homeless population to date say they encountered nearly 700 people whom homeless advocates did not know much about.

Nearly 850 people took the survey and only about 150 of them were already in the system, said Providence College professor Eric Hirsch, an expert on homelessness who oversaw the count at the state’s three largest shelters.

Homeless advocates now have records for most of the state’s vulnerable homeless population and can prioritize these individuals for housing and services, Hirsch said.

“This is such an important resource to have, and I just think that being able to prioritize people based on their vulnerability is going to save a lot of people’s lives,” Hirsch said this week after seeing the preliminary survey results.

Past surveys simply counted those sleeping outside and in emergency shelters. Advocates believe the new effort will help them figure out how people ended up on the streets, so they can connect the homeless with the most appropriate services and housing options.

The 60-question survey asked about a person’s background, medical care, general well-being and daily life, including among other questions, whether respondents experienced childhood trauma and if they owe anyone money.

Hirsch said he had hoped for 400 to 500 completed surveys, but with about 450 volunteers across the state, they found hundreds more.

Of the single adults surveyed, roughly one-quarter need subsidized housing and services to help them stay in that housing and about half need short-term help with housing expenses and some services, Hirsch said. The remaining people do not have any serious health or substance abuse problems. The data for the families has not yet been analyzed.

The survey was conducted over three nights in mid-November. Rhode Island is among 67 states and communities selected to participate in a nationwide campaign to end veteran and chronic homelessness in two years.

The national nonprofit Community Solutions developed the survey and organized the campaign.

Last year, about 4,450 people were homeless in Rhode Island, according to state data. Of that total, about 800 were considered chronically homeless and nearly 300 were veterans.