SANTA CRUZ (AP) — The mother of a missing 8-year-old girl pleaded for her safe return Monday as search efforts grew to include federal authorities.

Madyson Middleton vanished Sunday afternoon from an artist community and housing center in a Northern California beach town where she lives with her mother.

She was last seen riding her new, white scooter in the Tannery Arts Center courtyard, a place where children — both residents and those taking art and dance classes — frequently play. But at about 5 p.m. her mother realized she was gone.

Madyson’s parents met with investigators Sunday night and again Monday at police headquarters before speaking with reporters outside; her mother Laura Jordan they said they were very worried and wanted Madyson home.

“I can’t explain how difficult this is,” said Jordan, who had searched through the night for her little girl.

Jordan said she’s looked at surveillance video from their housing complex that watched Madyson’s last minutes before she disappeared. Police have said she was last seen on video surveillance at 4:12 p.m.

Almost 24 hours after her disappearance, Santa Cruz Police Chief Kevin Vogel said their search, for now, was focused on the Santa Cruz area.

“We’ve got a bunch of people out there looking for Maddy,” Vogel said.

Jordan has walked the edges of the courtyard, and police have twice conducted a door-to-door search of the entire complex, as well as a homeless resource center and shelter across the street.

Beyond the 8-acre property, searchers from throughout the state are now in boats, helicopters, on foot and bike, with dogs and cameras, searching for the girl. The FBI, as well as sheriffs from San Mateo and Santa Clara counties, are assisting.

FBI spokeswoman Laura Eimiller confirmed the FBI was assisting, but she said she would defer to Santa Cruz police for any additional details about the case.

Authorities weren’t sending volunteers onto adjacent hiking and biking trails for fear of disturbing potential evidence, but hundreds of volunteers showed up and were looking for her in neighborhoods and streets.

“This is our town, and this just shouldn’t happen here. We all should do everything we can to find this girl,” David Giannini said.

Authorities are using dogs to search nearby woods and parks and the San Lorenzo River levee. Helicopters are searching the forest and the coastline, and the U.S. Coast Guard has been scouring the ocean 2 miles from where she was last seen.

The 4-foot-tall, 50-pound child has long brown hair, which was pulled to the side in a braid, and dark eyes. She was wearing a purple dress, black leggings, black flip-flops and a black helmet.

She lived with her mother at the Tannery Arts Center, a public-private nonprofit project that includes 100 affordable loft apartments for artists and their families, a café, and dance and art studios on eight acres.

The property, a former leather tannery, is managed by The John Stewart Company. John Stewart, the company’s chairman, said they are fully cooperating with authorities and turned the surveillance footage over to authorities Sunday night.

Site manager Warren Reed said the property is located in a very busy area, with a number of businesses and a major construction project nearby.

It’s open to the public, and Reed said many people pass through to access a pathway that runs along the San Lorenzo River to the coast.