The endangered rhinos, two adults and a calf, were found at the Mara Triangle on Tuesday night.
There are 49 black rhinos in Maasai Mara, according to Mara Conservancy, which manages the Mara Triangle.
The Kenya Wildlife Service has opened investigation into mysterious deaths of three black rhinos in the Maasai Mara National Reserve in Narok.
The endangered rhinos, two adults and a calf, were found at the Mara Triangle on Tuesday night.
Some officials suspected that the rhinos might have consumed a poisonous plant, while others said that the animals died of natural causes.
An official at the KWS, who declined to be named as he is not authorised to speak to the press, overruled any possibility of poaching.
Preliminary investigations show that the rhinos belonged to the same family.
“We have taken samples from their bodies to the KWS laboratories in Nairobi to establish the cause of their deaths,” he added.
According to the Narok County Commissioner George Natembeya, one of the rhinos was 57 years old while the mother of the calf is believed to be aged between 15 and 20.
Mr Natembeya said KWS Narok Senior Warden Dickson Ritan is leading a team of investigators and a comprehensive report would be issued after the lab report is released.
No rhino death has been reported in the reserve situated in southwestern Kenya in the last two years.
In 2016, a black rhino was found dead in the reserve near the Kenya-Tanzania border with its horns missing.
Black rhinos are endangered species and are under threat from poachers.
There are 49 black rhinos in Maasai Mara, according to Mara Conservancy, which manages the Mara Triangle.
In 1971, the park had 120 black rhinos but the number dropped to due to poaching.
In 2015, KWS launched a forensic lab to help monitor cases of poaching.
In January 2016, the US government signed a memorandum of understanding on national conservation and management between the US Department of Interior and USAID, and Kenya’s Ministry of Environment and Natural Resources, to help improve surveillance technology, train wildlife rangers and share information as the best tools to counter poaching.
