Two immigration attorneys and two reporters told the Los Angeles Times they were not allowed to enter Mexico.

All four told the newspaper that they were held by Mexican immigration authorities and sent back to the U.S., saying that a foreign government flagged their passports.

Nora Phillips and Erika Pinheiro, the attorneys who were not allowed into Mexico, are on the board of directors of a nonprofit called Al Otro Lado. Al Otro Lado sued Customs and Border Protection in 2017, saying the agency illegally prohibited people from seeking asylum, according to the L.A. Times.

“I think this is retaliation,” Phillips told the newspaper.  “I think this is because we sued the U.S. government. I think it’s that we’re pointing out gross, flagrant human rights violations being committed by the U.S. government, and they don’t like that.”

One of the journalists denied entry, photographer Kitra Cahana, said she was told “the Americans” were behind the alert on her passport.

Photographer Daniel Ochoa of the Associated Press said he was also not allowed into Mexico. Both he and Cahana photographed the migrant caravan, whose members traveled through Mexico in the hopes of settling in the U.S.

The State Department declined to comment.

U.S. Customs & Border Protection said the Mexican government should be contacted.

“CBP did not pass any form of security alerts to the Mexican government on these individuals. They were both processed back into the United States without incident.”