Desperate for help and unsure whether traditional rescue efforts will come through, Harvey victims are using social media to share maps of their location and photos of themselves trapped on rooftops and inside buildings.

“Need help in NE Houston! Baby here and sick elderly!” one user posted on Twitter along with her address late Sunday.

Another woman, Alondra Molina, posted Monday on Facebook that her sister was desperate for a rescue for herself and her four children, including a 1-year-old.

“Please if someone could at least get them out of the city me and my mom will come get them,” Molina wrote. “The roads are just all blocked and we can’t get in.”

Annette Fuller took a video when she began fearing for her life on Sunday. She was on the second floor of a neighbor’s home along with the residents of three other houses, including five children, as water rose and hit waist level on the first floor.

“We called 911 and it rang and rang and rang and rang,” Fuller said Monday after the water receded and she managed to return safely to her single-story home.

“There’s just no agency in the world that could handle Harvey,” she said. “However, none of us were warned that 911 might not work. It was very frightening.”

Fuller’s two daughters, who live in Austin and Dallas, posted her video to Facebook after their mother texted it to them, and the post went viral.

“Social media, in some ways, is more powerful than the government agencies,” Fuller said.

A nursing home in Dickinson, a low-lying city 30 miles (48 kilometers) southeast of Houston, quickly became the face of the crisis after its owner took a photo of residents , some in wheelchairs, up to their chests in water.

The nursing home owner, Trudy Lampson, sent the photo to her daughter, whose husband posted it Sunday to Twitter, where it’s been retweeted about 4,500 times.

The photo was so dramatic that many users denounced it as fake. The nursing home residents were saved the same day.

“Thanks to all the true believers that re-tweeted and got the news organizations involved,” Lampson’s son-in-law, Timothy McIntosh, posted later in the day. “It pushed La Vita Bella to #1 on the priority list.”

Not only are the people who need rescuing relying on social media for help, volunteers and police departments alike are posting their phone numbers and instructions on Twitter and Facebook so people can get more immediate help.

An unofficial battalion of volunteers called the Cajun Navy who brought small boats to Houston posted on Facebook that people who need rescuing should download the Zello cellphone app to find rescuers close to their area.

“This will connect you with officials on the ground there that can navigate help your way. PLEASE SHARE!” said the post, which has been shared more than 12,000 times since Sunday night.

Harris County Sheriff Ed Gonzalez tweeted early Sunday that a woman was going into labor and shared the address. An hour later he updated his followers that the woman had been taken away in an ambulance.

More than any other natural disaster, Harvey has made it clear that social media has revolutionized the search-and-rescue process, said Karen North, a professor of social media at the University of Southern California.

“And what’s really fascinating is that this is not emergency services experts creating strategic systems to rescue people,” North said. “This is evolving organically … Not only can people reach out to 911 but to friends and family elsewhere who can not only reach out to 911 but directly to rescuers in the location where the person needs help.

“It’s really just the idea of taking technology designed for one purpose and applying them to a disaster situation,” North said.

Fuller said if the water rises again at her home, she won’t bother calling 911 and will post directly to social media.

“If I was desperate, I’d put it in a public Facebook site and say, ‘Somebody please help,’ and hope that somebody was looking,’” she said.

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Associated Press writers Regina Garcia Cano in Las Vegas, Alina Hartounian in Phoenix and Bob Eller in Chicago contributed to this report. Myers reported from Los Angeles.

Follow Myers on Twitter at https://twitter.com/AmandaLeeAP