The mayor of a town in the Mexican state of Oaxaca and two officials in her administration have been arrested over the disappearance of an anti-corruption activist who went missing after a protest outside the local town hall. Claudia Uruchurtu Cruz, 48, whose sisters live in Sheffield, disappeared on 26 March after participating in a demonstrations over allegations of arbitrary detention by local police in the municipality of Nochixtlán, about 375km south-east of Mexico City. Uruchurtu left the council office protest on her own, according to family, but was allegedly grabbed and forced into a red truck as she walked away from the scene. The vehicle was later found parked on municipal premises and identified as a municipal vehicle, according to family. The three suspects were taken into custody on Friday morning after an investigation into “the forced disappearance”, the Oaxaca state prosecutor’s office said in a statement. The suspects were not named, but Mexican media identified the mayor as Elisabeth Victoria Huerta of Nochixtlán and said the local police chief was among the other detainees. Uruchurtu’s three sisters: Elizabeth, Hayde and Sara said in a statement on Friday that she had run afoul of local officials, “when [she] publicly and directly questioned [them] and started to incessantly denounce arbitrary and corrupt acts by municipal authorities”. “She did things by the book,” said Chris Roast, Claudia’s brother-in-law told the Guardian from Sheffield. “She had a stack of paperwork a metre high” and had made complaints to the proper state and federal authorities, he added. “Claudia was an activist and she accused the mayor of a lot of corruption.” The arrests in Oaxaca made national news in Mexico as the mayor belongs to the same political party as President Andrés Manuel López Obrador – commonly called Amlo. Amlo won office in 2018 promising to put an end to rampant corruption and political repression. Mexican politicians and police routinely harass and intimidate citizens and journalists who denounce corruption. Last month a group of British MPs wrote to the foreign secretary, Dominic Raab, urging the UK government to help in the search for Uruchurtu.