We present Spitzer IRAC, NOAO 2.1 m Flamingos, Keck NIRC, and FCRAO SEQUOIA observations of the massive star-forming complex S254-S258, covering an area of 25 0 ; 20 0 . Using a combination of the IRAC and NIR data, we identify and classify the young stellar objects ( YSOs) in the complex. We detect 510 sources with near-or mid-IR excess, and we classify 87 Class I and 165 Class II sources. The YSOs are found in clusters surrounded by isolated YSOs in a low-density distributed population. The ratio of clustered to total YSOs is 0.8. We identify six new clusters in the complex. One of them, G192.63-00, is located around the ionizing star of the H ii region S255. We hypothesize that the ionizing star of S255 was formed in this cluster. We also detect a southern component of the cluster in H ii region S256. The cluster G192.54-0.15, located inside H ii region S254 has a V LSR of 17 km s À1 with respect to the main cloud, and we conclude that it is located in the background of the complex. The structure of the molecular cloud is examined using 12 CO and 13 CO, as well as a near-IR extinction map. The main body of the molecular cloud has V LSR between 5 and 9 km s À1 . The arc-shaped structure of the molecular cloud following the border of the H ii regions and the high column density in the border of the H ii regions support the idea that the material has been swept up by the expansion of the H ii regions.

We present Spitzer, NIR and millimeter observations of the massive star forming regions W5-east, S235, S252, S254-S258 and NGC7538. Spitzer data is combined with near-IR observations to identify and classify the young population while 12 CO and 13 CO observations are used to examine the parental molecular cloud. We detect in total 3021 young stellar objects (YSOs). Of those, 539 are classified as Class I, and 1186 as Class II sources. YSOs are distributed in groups surrounded by a more scattered population. Class I sources are more hierarchically organized than Class II and associated with the most dense molecular material. We identify in total 41 embedded clusters containing between 52 and 73% of the YSOs. Clusters are in general non-virialized, turbulent and have star formation efficiencies between 5 and 50%. We compare the physical properties of embedded clusters harboring massive stars (MEC) and low-mass embedded clusters (LEC) and find that both groups follow similar correlations where the MEC are an extrapolation of the LEC. The mean separation between MEC members is smaller compared to the cluster Jeans length than for LEC members. These results are in agreement with a scenario where stars are formed in hierarchically distributed dusty filaments where fragmentation is mainly driven by turbulence for the more massive clusters. We find several young OB-type stars having IR-excess emission which may be due to the presence of an accretion disk.