U.S. immigration authorities canceled the visas of 27 people tied to cruise ships in enforcement actions that U.S. Customs and Border Protection linked to allegations involving child sexual abuse images, the agency said. U.S. Customs and Border Protection said authorities boarded eight cruise ships in late April and determined the people were involved in “the receipt, possession, transportation, distribution, or viewing” of such images.

In its statement, U.S. Customs and Border Protection said the agency canceled the visas of those involved and returned them to their home countries. The agency did not say whether any passengers aboard the ships were believed to be victims, and it did not detail which ships were boarded, why those ships were targeted, or where the operations took place.

The agency’s statement said no additional information was available. At least some of the ships had docked in San Diego, according to the account described by the Associated Press.

Disney Cruise Line said in a separate statement that it has a “zero-tolerance policy for this type of behavior and fully cooperated with law enforcement. While the majority of these individuals were not from our cruise line, those who were are no longer with the company,” the company said.

Immigrant and workers’ rights groups said they had been trying to obtain more information about the workers and the reasoning behind the enforcement action. Benjamin Prado, with Unión del Barrio, said his group held a news conference Tuesday in San Diego after it previously received only a generic statement from Customs and Border Protection.

Prado said the later statement released to news organizations this week “did not appear to be on the agency’s website,” and he said the information should be accessible. Prado said his group wants “to better understand what kind of monitoring or surveillance might have been occurring ahead of the workers being detained and whether due process rights were followed,” adding that the group was skeptical of the information the agency provided.

“At this point, we doubt, we question their claims and so we do want to follow up with some of these workers to find out exactly what took place,” Prado said. The Associated Press report also said Customs and Border Protection has said a criminal charge is not required for someone’s visa to be revoked.