Bones wrapped in a polythene bag were found on a plot in Haridevpur, on the southern fringes, on Monday morning.

A few labourers who have been hired for construction work on the plot — in the Satyen Park area — spotted the polythene bag containing a skull and other bones.

Forensic officials who visited the spot said an anthropological test would reveal whether they were human bones and what caused the death.

A preliminary probe by forensic officials suggests that bones have not undergone natural decomposition. They were possibly manually cleaned, suggesting the bones were dumped on the spot.

“Usually when bones are recovered, they are found with remains of flesh on them. The fact that these bones were fresh and had been cleaned of their marrow suggests they had been used for medical purposes,” an officer of Haridevpur police station said.

“The bones will undergo an anthropological examination for determining the age and gender and whether they are human bones or not,” said M.W. Raja, senior scientist of the state forensic sciences laboratory.

Forensic experts have collected samples of the soil where the bones were found for testing. According to a forensic expert, the composition of the soil changes if a body is allowed to decompose there.

Also, an overwhelming stench emanates from a spot where a body decomposes. People in the locality said they did not see or smell anything unusual in the area over the past few days.

“We dump garbage here. No unusual activity was seen here. We heard about the bones in the morning,” said a resident.