Guwahati, Nov. 1: The authorities of Manas National Park have arrested four persons, Raju Boro, Bwlwgra Daimary, Milan Basumatary and Kanto Boro, in connection with the seizure of a tiger skin today.

Those arrested are reported to be involved in tiger poisoning and all four hail from Betbari of Bhuyanpara range.

Sources said investigation had revealed that the tiger was killed last week." Investigation is on to find out how the tiger was poisoned," an official said.

Officials are taking help of a database to identify the tiger through its stripes. An identification number is given to each tiger to help distinguish it from others.

A source said the tiger, which was poisoned, was the one captured from Geleky in Sivasagar in 2010 and brought to Manas.

A source said the entire operation was planned at Betbari, which is an area of large-scale encroachment in Manas. "If the encroachment is not controlled and tackled seriously, wildlife will be at risk," the source said.

"It is difficult to understand why the eviction has not materialised till now. The encroachment has been happening for a long time," the source added.

The seizure of the tiger skin has put the national park back in the spotlight. There had been no reports of tiger poaching from Manas for quite a while.

Officials of the Wildlife Crime Control Bureau and the National Tiger Conservation Authority are also investigating the case.

A National Tiger Conservation Authority team will be going to Manas tomorrow .

Twenty-one tigers were camera-trapped during a trans-boundary tiger-monitoring programme conducted across Manas National Park in India and Royal Manas National Park in Bhutan 2015.

Of the 21, 11 were obtained from Royal Manas National Park Bhutan and 14 from India. Four tigers were found to be common to both the landscapes.

ADDITIONAL REPORTING BY PREETAM B. CHOUDHURY FROM KOKRAJHAR