Shimla, March 3 (IANS) At least three pilgrims from Punjab were killed and 47 injured Wednesday when the truck they were travelling in overturned in Himachal Pradesh's Una district as they were returning from a Sikh shrine, an official said.

'The truck overturned in the afternoon near Mairi village in Una. The pilgrims were returning to Punjab after paying obeisance at the Dera Baba Vadbhag Singh shrine,' Deputy Commissioner K.R. Bharti told IANS over telephone.

He said most of the injured were admitted to the district hospital at Una.

'Four seriously injured were sent to the PGIMER (Post-graduate Institute of Medical Education and Research) at Chandigarh,' he said, adding that most of the passengers belonged to Tarn Taran district.

The cause of the accident is yet be ascertained, Bharti said.

According to the police, the truck was converted into a double-decker by fitting wooden planks so that more passengers could be accomodated.

Though it is illegal, double-decker trucks carrying passengers is a common sight in Himachal Pradesh, especially during religious festivals.

The accident spot is some 175 km from Shimla.