Indian authorities on 21 September ordered a probe into the deaths of a dozen endangered wild Asiatic lions, half of them cubs, over the last 10 days, officials said.
One lioness died after preying on a poisoned boar while eight others lions died of an infection in the lungs and liver.
Three cubs were killed in infighting while other three passed away in the course of treatment.
Gujarat officials have sent the lions' carcasses to a veterinary hospital for further analysis into the cause of infection.
"Primarily the deaths appear due to natural causes or some infection," Vijay Chaudhary, forest department official, told AFP.
Listed as critically endangered in 2000, wild Asiatic lions reside only in one Indian forest -- the Gir Sanctuary spread over 1,400 square kilometres (545 square miles) in the western state of Gujarat.
The lions, a major tourist attraction in the state, have been a target of poachers in the past.
Experts said that the deaths cannot be dismissed as part of a natural cycle.
"There needs to be some preventive action by tracking the pride of lions in the area and checking them for infections," Priyavrat Gadhvi, a wildlife expert and members of state wildlife board in Gujarat, told AFP.
According to the latest lion count done in 2015, there are 521 Asiatic lions. About 10 of them died in floods in 2016.