The Assam forest department on Sunday released six feral horses at Dibru-Saikhowa National Park, which were rescued from Makum bypass in Upper Assam’s Tinsukia district on March 2.

A source said the horses were allegedly being taken to Guwahati by a gang of smugglers.

The source said the department detained four persons in connection with the case and an investigation was on.

Forest officials are not yet sure whether the horses were captured by the smugglers from the national park or from the outer areas.

Another source said the horses were allegedly being taken for riding at a polo club and some senior government officials are suspected to be involved.

The department, however, have not revealed the names of the detained persons.

The horses are suspected to be from the Guijan range of the park and further investigation was on to verify the matter.

Dibru-Saikhowa National Park is spread across Dibrugarh and Tinsukia districts in Upper Assam, around 521km from here.

It is designated as a biosphere reserve and houses many endangered species and is rich in fish diversity.

It is also known for its huge population of feral horses. Feral horses are free-roaming animals of domesticated stock. Some populations of feral horses also live in the wild.