In September 2023, the first infections with a novel lineage of mpox were detected in South Kivu. Since then, the virus has spread regionally, nationally and internationally. As part of continued efforts to understand the mpox ecology and epidemiology, the South Kivu district of public health and partners have set up systematic case finding and follow-up, including strain characterisation through PCR and sequencing. Samples were collected from 595 hospitalized patients with a confirmed mpox virus infection. A clade differentiating RT-PCR showed that 545 (92%) of samples were positive for clade Ib but also remarkably that Clade Ia infections were diagnosed for the first time in South Kivu. First detected in cases in week 7 in Kamituga, 50 cases were identified over the whole study period (8,40% of all cases). Phylogenetic analysis of initial cases revealed introductions of clade Ia into the South Kivu province alongside the continuation of the clade Ib mpox virus outbreak. These findings underscore the increasing complexity of clade I mpox virus outbreaks in the DRC.