EL PASO, Texas (AP) — A large group of migrants in Mexico who were poised to barge into the U.S. over the weekend were blocked from crossing a bridge leading from Ciudad Juarez, Mexico, to El Paso, Texas, a U.S. Customs and Border Protection spokesman said.

The migrants were “posing a potential threat to make a mass entry,” and physical barriers were put up to restrict their entry at the Paso Del Norte International Bridge on Sunday afternoon, spokesman Roger Maier said in a statement to The Associated Press on Monday.

Barricades also were used in El Paso for a short time Sunday afternoon at other border crossings including the Bridge of Americas and the Stanton-Lerdo bridge, Maier said.

Video of the scene at the Paso Del Norte bridge on Sunday showed hundreds of migrants brush past Mexican National Guard officers on the Mexican side, some carrying children on their shoulders. Many appeared to be Venezuelan, by their accents.

Shouting “We want to get through!,” the migrants ran up to the center line of the bridge, where U.S. authorities had erected concrete and plastic barriers strung with concertina wire.

The migrants were stopped by the barrier, and remained on the Mexican side, shouting “Open up for us!” to the U.S. officers. After a time, the migrants ran back toward the Mexican side.

Traffic was reopened and flowing in both directions as of Sunday evening, Maier said. It wasn’t immediately known what caused the attempted mass crossing. A message seeking comment was left with the mayor’s office in El Paso.

The rush across the bridge may have been sparked by false rumors, said Camilo Cruz, who works with the U.N. migration office in Ciudad Juarez.

Cruz said there was “a rumor that they were going to let them cross massively, particularly people who arrived with children.”

Cruz said the rumors are a recurrent problem. About a month ago, messages began circulating “that there were going to be buses on the U.S. side to take them to Canada … and when they arrived, they were told it was a lie.”

The worst thing, Cruz said, is that migrants often leave the shelters where they are staying to attend such mass crossing attempts, only to find the shelters full when they return.

Many of the migrants on Sunday appeared to be asylum seekers. One woman held out what appeared to be an appointment slip at the barricade. Migrants seeking asylum, a legal immigration pathway for people fleeing persecution in their own country, have been frustrated by newly-implemented limits on those showing up at the southwest border, as many Venezuelans do.

There has been frustration with the U.S. government’s CBPOne mobile app for making appointments to apply for asylum, which has been overloaded since the Biden administration introduced it Jan. 12. New appointments are available each day at 6 a.m., but migrants find themselves stymied by error messages.

Also causing frustration is a pandemic rule, scheduled to end May 11, that denies migrants a chance to seek asylum on grounds of preventing the spread of COVID-19. Under the public health rule, known as Title 42, Mexico recently began taking back Cubans, Haitians, Nicaraguans and Venezuelans who crossed.

In addition, the Biden administration has said it will generally deny asylum to migrants who show up at the U.S. southern border without first seeking protection in a country they passed through.

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