A double mutation has been detected in 61 per cent of the total 361 COVID-19 samples tested between January and March this year, a genome sequencing  expert claimed on Wednesday even as he raised doubts over the methods of sample collection being adopted by authorities in Maharashtra, which is worst affected by the pandemic.

However, experts in genome sequencing and cell science said that such a small sample cannot be considered an indication of the spread of the mutated virus. These 361 samples were tested at the genome sequencing laboratories in Maharashtra.