Shimla, Aug 11 : The Chandigarh-Shimla national highway, the main lifeline of the Himachal Pradesh capital and upper areas of the state, was closed again after a massive landslide in Solan district early Friday, police said. The newly laid highway has been closed near Chakki ka Mod, the sinking zone that kept the highway shut for nearly a week. The highway was reopened for traffic on Tuesday. Authorities have deployed men and machinery to make the highway motorable. Experts blame unscientific road construction for the frequent landsides on the highway at several points between Parwanoo and Solan towns. Last week, a 40 metre-long road was completely washed away near Chakki ka Mod. The police directed commuters to use alternative roads like Parwanoo-Jangeshu-Kala Amb-Nahan-Kumarhatti or Baddi-Nalagarh-Ramshehar-Kunihar to travel towards Shimla from Chandigarh. /IANS