Mexico’s president, Andrés Manuel López Obrador, has blamed protesting migrants for causing a fire at an immigration detention centre that has killed at least 39 people in Ciudad Juárez, a Mexican city on the US border.

Images of the aftermath showed dozens of lifeless bodies on the ground, some covered by silver thermal blankets. Television footage showed emergency workers attending to stunned survivors, who sat on white sheets gasping for breath.

Speaking at his daily press conference, López Obrador said the “very regrettable and very sad” disaster had been triggered on Monday night when migrants being held at the detention centre set fire to their mattresses, apparently in protest at their anticipated deportation. “They didn’t imagine it would lead to this terrible tragedy,” added Mexico’s president, who said most victims were from Central America and Venezuela.

Millions of Venezuelans have abandoned their economically devastated country in recent years in search of a better life in other South American countries or the US.

The newspaper El Universal said immigration officials had spent the hours before the fire, which broke out at about 10pm on Monday, rounding up Venezuelan migrants who had been begging for money on the streets of Ciudad Juárez, which is just over the US border from El Paso, Texas. Some of those migrants are believed to have been transported to the immigration centre where the fire broke out.

One of those detained men was Orlando Maldonado, a 30-year-old from the Venezuelan city of Guarenas, who was picked up by immigration officials at about 2pm on Monday afternoon and was inside the building when the fire happened. “We don’t know if he’s dead or alive,” said his friend, Julianny Lopez, 23, as she waited outside the detention centre with other migrants for news of their missing loved ones.

“He asked me to not leave him alone. I will never forget his words,” said Maldonado’s 23-year-old sister, Katiuska Marquez, who was also detained but later released because she was caring for a toddler.

El Diario de Juárez, a local newspaper, reported that preliminary investigations by forensic teams suggested that a group of male inmates had barricaded themselves inside the wing for male prisoners and started a fire. The newspaper said all of the fatalities were thought to have been men.

The Los Angeles Times said a federal Mexican official had told its reporters that the migrants were protesting because 68 people had been confined to a cell intended for a maximum of 50 and deprived of drinking water.

The local news website Norte Digital said several of the victims had been found in the bathrooms of the detention centre, where inmates are believed to have sought refuge from the flames.

The fire – reportedly one of the deadliest ever to hit an immigration detention centre in Mexico – is the latest disaster this year to highlight the multitude of dangers facing the hundreds of thousands of migrants and refugees who continue to flock to the US’s southern border each year after a perilous journey through South and Central America.

Last month at least 39 migrants died in a bus accident in Panama after trekking for days through the Central American country’s southern jungles on their way to the US.

The victims included citizens of Venezuela, Ecuador and Haiti. According to CNN Español the bodies of 13 victims – from Eritrea, Haiti and Nigeria – were buried by authorities last week after their families did not claim them.

The fire has also highlighted the increasingly tough migration policies that have been put in place by Joe Biden’s administration. Limits on the number of people allowed to seek asylum have left cities along Mexico’s northern border overwhelmed by the number of people trying to cross into the US, with many forced to sleep on the streets or inside churches or packed shelters.

“As Mexico receives historic numbers of new asylum claims and the US continues to implement policies that push asylum seekers back into Mexico, humanitarian infrastructure in the country is increasingly strained and more people are stuck in highly vulnerable situations,” the International Rescue Committee said in a statement.

“These risks are particularly tangible in cities along the US-Mexico border, such as Ciudad Juárez, which for years have seen increasing numbers of displaced people as new and stricter border policies have been put in place.”