3 arrested in Mexico City bar kidnapping case September 12, 2013 -- Updated 2135 GMT (0535 HKT) Families of missing haunted by mystery Federal prosecutors say they arrested three additional suspects The mysterious mass kidnapping in May jolted Mexico City Victims' family members have said they don't trust authorities Read this story in Spanish at CNNMexico.com Mexico City (CNN) -- Mexican authorities say they've arrested three additional suspects connected to the kidnapping of 13 youths from a bar in the country's capital. Federal prosecutors told reporters that Jonathan Robles, Pedro Francisco Paz Lopez and Fernando Fernandez Sanchez are suspected in connection with the kidnapping and killing of the youths. The mysterious mass kidnapping from the Heaven after-hours bar in May drew international attention after furious family members protested, claiming authorities weren't taking the case seriously. The allegations have sparked concerns about whether violence has surged into Mexico City, where residents largely have been spared from drug war casualties seen in other parts of the country. Last month authorities said they'd found the missing youths' bodies in a shallow grave near Mexico City. Mexico City Prosecutor Rodolfo Rios Garza said last month that the motive for the killing was revenge for a slaying that occurred in another bar in the capital. At least seven other suspects have been arrested in the case. Victims' family members have said they don't trust Mexican authorities and have called for an independent international investigation of the case. CNN en Español's Fidel Gutierrez and CNNMexico.com contributed to this report.