Jaipur, Dec 22 (IANS): Authorities in Rajasthan have started an investigation into the sudden deaths of as many as 16 deer at a zoo in Kota, officials said Friday.

"The zoo employees spotted some of the deer lying motionless and others moving around frantically, apparently in pain, in their enclosures. They immediately informed their seniors," said a senior forest department official said.

The official told IANS that the employees noticed the tragic incident at the Kota zoo, some 300 km from here, around 6 a.m. Thursday.

Of the 16 dead animals, 10 were female and at least five of them were pregnant, officials said. Only five deer in the enclosure have survived and have now been put under medical observation.

The autopsy on the dead animals was conducted in the zoo complex Thursday evening.

"As per the preliminary post-mortem report, the doctors found infection in the lungs of all the dead animals. They died of asphyxia as they could not breathe properly due to the infection," the official said.

He added that the sudden dip in the temperatures Wednesday night could be the reason behind the deaths.

"The reason behind the sudden deaths is yet to be ascertained. Investigation is on. The arrangements made by the zoo authorities to save the animals from the cold during nights is being probed," the official said.

He added that it is also being probed whether there had been any negligence on part of the night duty guards.