The initial probe found that the “Flight of the Gibbon” tour was operating without a tourism business licence.

District chief Pattaraporn Laijud yesterday led police and related officials to inspect the facility and its documents.

She informed the business about the suspension of its operations. The results of the investigation will be submitted to the provincial governor.

The Provincial Police Region 5 acting deputy chief, Maj-General Pithaya Sirirak, said police would determine if the incident – in which two adults in their 40s were also seriously injured – was caused by the recklessness of staff.

He believes the accident would not have occurred if staff had followed the required steps.

He said the injured tourists were covered by personal travel insurance policies and the zip-line operator had accident insurance.

Pithaya said relevant agencies would probe whether the business had a tourism business licence and whether the leased land it was located on had encroached on forestland.

The Forest Resource Management Office 1 (Chiang Mai) is checking with the Land Department because the leased land appears to be a fertile forest.

It is understood that the Flight of the Gibbon tour has 31 stations covering five kilometres, with each station handling up to 10 visitors at a time with the average zip-line speed of 20.40km per hour.