"After the accident that occurred in Chiapa de Corzo, I inform you that unfortunately 49 people died at the scene and 5 more died while receiving medical attention in hospitals," Chiapas Gov. Rutilio Escandón tweeted. "We have 105 injured (83 men and 22 women), care for the injured continues."
On Friday, Escandón updated that one more person died, bringing the death toll to 55.
The truck carrying the migrants crashed on a sharp curve outside the city of Tuxtla Gutierrez, according to Luis Manuel Garcia, head of the Chiapas civil protection agency.
Chiapas' civil protection agency said on Twitter that the tragedy was the result of a "car accident of two trucks traveling on the Belisario Domínguez Bridge and Ribera Cauharé in Chiapa de Corzo."
"I deeply regret the tragedy caused by the overturning of a trailer in Chiapas carrying Central American migrants. It's very painful. I embrace the families of the victims," Mexican President Andres Manuel Lopez Obrador tweeted.
Mexico's National Institute of Immigration also confirmed the incident on Twitter, saying it "regrets the death of migrants in the tragic accident that occurred in Chiapas."
It also said it is coordinating efforts with national, state and municipal authorities to provide consular assistance, identify bodies, cover funeral expenses and facilitate the repatriation of remains to countries of origin.
"Humanitarian attention that will be granted to the survivors will be accommodation, food and in case they accept, Visitor Cards for Humanitarian Reasons," the institute wrote. "The INM will assist in the investigation of the accident."
The victims appeared to be migrants from Central America, The Associated Press reported.
Central American migrants fleeing poverty and violence often take dangerous routes through Mexico to reach the United States, according to the United Nations. Smugglers sometimes cram migrants into large vehicles in extremely dangerous conditions to get them over the border.
The Biden administration has been criticized for reinstating Trump-era policies that make seeking asylum in the U.S. more difficult, pushing migrants into dangerous situations, immigration advocates say,
Vicki Gaubeca, director of the Southern Border Communities Coalition, told ABC News in a past interview that migrants with legitimate claims of asylum are often bypassing ports of entries out of fear they'll be expelled due to the tough immigration policy.
"This has been the worst policy that was implemented by Trump that -- much to our surprise and disappointment -- has been continually used by the Biden administration," Gaubeca said.