GUADALAJARA — Members of the Guerreros Buscadores, a collective that searches for missing people in areas of Mexico affected by drug cartel violence, uncovered human remains in a residential area of Guadalajara on a recent Tuesday after receiving an anonymous tip. The searchers recovered part of a skull, a jawbone, a bag of bones, a shoe, and a pelvis before reporting the find to federal officials.

The tip came from an informant who reported a body buried in the area. The collective receives anonymous tips through its website and travels to the indicated locations. On the day of the search, Raúl Servín noticed a hole with small rocks between a wall and train tracks. The team used a metal rod called "the seer," which searchers stick into the ground to detect organic smells.

After recovering the remains, the searchers arranged the bones outside the pit, placing similar-looking bones separately to avoid mixing remains of different individuals. A searcher lit a candle at the edge of the pit. Another member of the group prepared to go live on Facebook to document the search, a practice that has previously helped searchers verify discoveries, including the use of a ranch by the Jalisco New Generation Cartel.

Servín used his panic button to contact federal officials, confirmed his identity with a password, and reported his findings and location. He requested hourly monitoring before calling the police.

"I don't get nervous anymore," Servín said. "There cannot be room for doubt."

Servín has been looking for his son, who disappeared eight years ago. Every Tuesday, he and three teammates load a van with picks, shovels, water, and lunches before venturing into search areas. He lost his job when he started searching for his son and now works as a waiter on weekends. The searchers wear personalized T-shirts bearing a photo of their loved one; Servín's reads "Searcher Dad." "I love soccer, but that's not going to stop me from going out to search," he said.

More than 130,000 people have been reported missing in Mexico since 2006, and nearly 20,000 missing people have been found dead since 2010. More than 70,000 unidentified remains are held in morgues and cemeteries across the country. Jalisco state, where Guadalajara is located, is a stronghold of the Jalisco New Generation Cartel and an epicenter of disappearances. Since 2010, at least 36 searchers have been killed, according to civil society organizations, with the most recent killing in mid-March.