TAPACHULA, Mexico (AP) — Around 3,000 migrants set out Sunday on what they call a mass protest procession through southern Mexico to demand the end of detention centers like the one that caught fire last month, killing 40 migrants.

The migrants started from the city of Tapachula, near the Guatemalan border. They say their aim is to reach Mexico City to demand changes in the way migrants are treated.

“It could well have been any of us,” Salvadoran migrant Miriam Argueta said of those killed in the fire. “In fact, a lot of our countrymen died. The only thing we are asking for is justice, and to be treated like anyone else.”

But in the past many participants in such processions have continued on to the US border, which is almost always their goal. The migrants are mainly from Central America, Cuba, Venezuela, Ecuador and Colombia.

Mexican authorities have used paperwork restrictions and highway checkpoints to bottle up tens of thousands of frustrated migrants in Tapachula, making it hard for them to travel to the US border.

Argueta said that when migrants look for work in Tapachula, “they give us jobs, perhaps not humiliating, but the one the Mexicans don’t want to do, hard work that pays very little.”

Organiser Irineo Mújica said the migrants are demanding the dissolving of the country’s immigration agency, whose officials have been blamed — and some charged with homicide — in the March 27 fire. Mújica called the immigration detention centres “jails.”

The roots of the migrant caravan phenomenon began years ago when activists organised processions — often with a religious theme – during Holy Week to dramatiae the hardships and needs of migrants. In 2018 a minority of those involved wound up traveling all the way to the US border.

This year’s mass walk began well after Holy Week had ended, but Mújica, a leader of the Pueblos Sin Fronteras activist group, called it a “Viacrucis,” or stations of the cross procession, and some migrants carried wooden crosses.

“In this Viacrucis, we are asking the government that justice be done to the killers, for them to stop hiding high-ranking officials,” Mújica said in Tapachula before the long walk began. “We are also asking that these jails be ended, and that the National Immigration Institute be dissolved.”

Some migrants carried banners or crosses reading “Government Crime” and “The Government Killed Them.”

The migrants made it only as far as the town of Alvaro Obregon, about 9 miles (14 kilometres) from Tapachula, before stopping to settle down and rest for the remainder of the day, after having walked from around dawn.

The migrants stretched out under a covered athletic court and under trees at a park in Alvaro Obregon. There was no sign at the start of any police attempt to block them.

Mexican prosecutors have said they will press charges against the immigration agency’s top national official, Francisco Garduño, who is scheduled to make a court appearance April 21.

Federal prosecutors have said Garduño was remiss in not preventing the disaster in Ciudad Juarez despite earlier indications of problems at his agency’s detention centers. Prosecutors said government audits had found “a pattern of irresponsibility and repeated omissions” in the immigration institute.

Six officials of the National Immigration Institute, a guard at the centre and the Venezuelan migrant accused of starting the blaze are already in custody facing homicide charges.