The husband of the owner and operator of the Bronx day care where a 1-year-child died of suspected fentanyl exposure appeared in California federal court to face charges, two days after authorities captured him in Mexico, officials announced.

Felix Herrera Garcia, who had been on the run since the child died on September 15, is the fourth person arrested and charged in connection with the suspected fentanyl exposure. The incident has rocked local leaders and sparked public outcry in New York.

Officials said a kilo of the poisonous and potent drug was stored on top of children's play mats, and more fentanyl was found beneath trap doors inside the room where the kids played and slept at the daycare, according to court records.

Herrera Garcia was charged with conspiracy to distribute narcotics resulting in death, and possession with intent to distribute narcotics resulting in death, records show.

CNN was unable to identify an attorney for Herrera Garcia, who is expected to be brought back to face the charges in federal court in New York.

"When it comes to protecting our communities and seeking justice, there are no boundaries, no safe havens, and no stones left unturned," Drug Enforcement Administrator Anne Milgram said in a statement.

The alleged mid-level drug dealer was taken into custody by US Drug Enforcement Administration officials and Mexican authorities after he was spotted on a bus in Sinaloa on Tuesday, law enforcement officials previously told CNN. He was arrested immediately upon entering the United States and went before a US Magistrate Judge in the Southern District of California, officials said.

"Herrera's arrest on the other side of the nation reflects our tireless pursuit of Herrera, who fled the daycare even as the children he abandoned inside were suffering from his poisonous trade," US Attorney for the Southern District of New York Damien Williams said in a statement.

Herrera Garcia got two phone calls from his wife, identified by authorities as co-conspirator Grei Mendez, after four children at the day care center began to show signs of an overdose on September 15, court documents show. Investigators say Mendez called him before she called 911, records show. She also placed a call to Herrera Garcia's cousin -- Carlisto Acevedo Brito -- who was also involved in the alleged conspiracy and was arrested, officials said.

Minutes before emergency responders arrived to help the poisoned children, Herrera Garcia is seen on surveillance exiting a back door of the day care center with two shopping bags full of what appear to be drugs, officials said.

One-year-old Nicholas Dominici died after the suspected fentanyl exposure at Divino Niño day care center. Three other children -- two 2-year-old boys and an 8-month-old girl -- were hospitalized after being exposed to the suspected fentanyl and suffered acute opioid intoxication, authorities said.

While law enforcement was searching for Herrera Garcia, they expanded their investigation and arrested yet another associate, identified as Renny Antonio Parra Paredes, 38, authorities said.

All are alleged to have been mid-level drug dealers who would cut the fentanyl with other drugs or even household items like baby powder, using the pressing machines found in the day care center to get the drugs packed and ready for distributors, a law enforcement official previously told CNN.