Immigration rights activists are protesting the detention of a prominent Washington-area organizer in Arizona after she appeared for what she thought was a routine hearing.

The Washington Post reports 32-year-old Alejandra Pablos was detained Wednesday when the legal permanent resident traveled to the Phoenix area to check in with immigration officials on a pending deportation case stemming from a felony conviction for driving under the influence. She'll be held until her next scheduled court appearance, in December.

Pablos is an organizer for the National Latina Institute for Reproductive Health. Institute associate director Margie Del Castillo says Pablos' supporters believe her activism made her a target of Immigration and Customs Enforcement. The agency denies it.

Actress and activist Alyssa Milano has circulated a petition supporting Pablos, which has amassed nearly 8,000 signatures.