(NewsNation) — Two Mexican polling workers were killed and one was kidnapped last Saturday while conducting internal polling for President Andrés Manuel López Obrador’s Morena party in southern Mexico, CBS News reported.

The kidnapped worker remains missing, but the country’s public safety secretary, Rosa Icela Rodríguez, announced three people were arrested in connection with the killings and kidnapping, the report said.

The three workers were working with two others in the town of Juárez, Chiapas, where the incident occurred. The other two employees were unharmed and safe.

The two workers killed were identified as 23-year-old José Luis Jiménez and 43-year-old Christian Landa Sánchez, according to a press release from Chiapas state prosecutors.

“With great pain, sadness and indignation, we regret and strongly condemn the murder of our colleagues Christian Landa Sánchez and José Luis Jiménez and we demand a thorough investigation from the corresponding authorities,” Mario Delgado, the leader of the Morena party, wrote on social media.

Rodríguez said three suspects were caught with the victim’s possessions, but it wasn’t confirmed whether robbery was the motive behind the attack, CBS reported. It was later added that there was a fourth suspect arrested in connection to the incident, Chiapas state prosecutors said.

The Chiapas state prosecutors said three of the four were Guatemalan and one was a Mexican citizen.

The two victims killed were allegedly discovered with handwritten signs from the Jalisco drug cartel threatening the government, according to multiple local reports.