ISLAMABAD, Dec. 21 (Xinhua) -- At least 11 people were killed and 20 others injured when a passenger bus met accident in Pakistan's east Punjab province on Thursday, local reports said.

The ill-fated bus, carrying 40 people, was on its way to provincial capital of Lahore from Rajanpur district when it met the accident, local TV channel Geo reported.

Police said that the accident happened due to low visibility caused by the heavy smog, adding that the driver was negotiating a sharp turn, but lost control over the vehicle due to low visibility.

Rescue teams said that the whole area has been engulfed by the smog, making them hard to carry out the rescue operation.

Plains of Punjab have been partially blanketed with the fog over the last couple of days, causing problems for the commuters early in the morning.

Local experts said that the smog this year has been caused by inland activities. Increased number of vehicles on roads, smoke from industries and mushroom-growth of housing societies in urban areas have caused the smog in the province.