(CNN) — At least 39 people died in a fire at a migration center in Mexico's northern border city of Ciudad Juarez, officials said Tuesday.

Authorities said the fire at the office of National Migration Institute (INM) occurred after they picked up about 71 migrants from the streets of the city.

The cause of the fire or the victims' nationalities have not been released by Mexico's National Migration Institute, who have launched an investigation into the blaze.

"It is with deep sadness and grief that we learned of the fire that occurred inside the INM in Ciudad Juárez," Andrea Chavez, Ciudad Juarez's federal deputy, tweeted on Tuesday.

We will wait for the official information and, from this moment on, we send our condolences to the families of the migrants. FGR initiated the investigation," Chavez said.

Body bags were lined up near the scene of the fire, which had been extinguished, Reuters reported a witness as saying. Most of the migrants at the center were Venezuelan, the witness added.

The blaze is one of the worst in recent years in Mexico, which is seeing record levels of crossings at its border with the US.

Earlier this year, the Biden administration ramped up efforts to curb the number of migrants crossings at the border.

In February, it released a new rule that largely prohibits migrants who traveled through other countries on their way to the shared frontier from applying for asylum in the US, marking a departure from a decades-long precedent in proposed regulations reminiscent of Trump-era policy.

CNN has reached out to Mexico's migration authorities for statement on the fire.

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