California investigators have revealed that they believe foul play was involved in the disappearance of San Francisco hotel worker Chantel Brooks.

Fairfield Police asked for help finding Brooks, 36, earlier this month after she vanished in the early hours of July 17 following a trip to CVS.

“Based on what detectives have learned during the investigation, it is believed Chantel’s disappearance involved foul play,” Fairfield Police said in a Facebook post Tuesday.

Brooks is a desk clerk at Le Nain Hotel in San Francisco’s Tenderloin District, according to NBC Bay Area. On July 17 at around 12:20 a.m., local time, Brooks was seen on surveillance camera leaving her job, Fairfield Police said in a previous Facebook post.

At around 1:45 a.m. that same day, Brooks was seen on camera leaving a CVS in Fairfield, where she lives, and approaching her car in the parking lot, according to authorities.

"When we first heard about it, we hit the ground running," Kevin Robinson, one of Brooks’ brothers, told NBC Bay Area. "Being her brothers, we're her first line of protection.”

“We're all on our knees together, praying,” he added.

Fairfield Police said they have conducted dozens of search warrants, multiple ground searches and extensive drone searches since Brooks went missing.

“The department is also working closely with the Solano County District Attorney’s Office while working through various leads in her disappearance,” the department wrote on Facebook Tuesday.

Brooks — who is 5 feet 6 inches tall and weighs 180 pounds — was seen wearing a baseball cap, red sweatshirt, gray sweatpants and brown furry boots when she disappeared. Her car is a black 2021 Infiniti QX50 SUV with a California license plate that reads 9SBB134.

Brooks was born and raised in San Francisco and came from a big family with 13 siblings as well as cousins around the Bay Area, Robinson said.

Her family has gone door-to-door in Fairfield to ask Brooks’ neighbors about what they know. On Thursday, they celebrated Brooks’ 37th birthday with a vigil in Fillmore-Turk Mini Park in San Francisco.

"She's warm and outgoing," Robinson said. "Everyone she meets remembers her."

Fairfield Police have asked anyone with information regarding Brooks's whereabouts to call the department directly at 707-428-7300 or email case26-7208@fairfield.ca.gov. People can also use the department’s anonymous tipline at 707-428-7600.

“Our investigation will remain active as we continue working to find Chantel and determine what happened to her,” Fairfield Police said. “We remain committed to providing answers to her family and our community.”