The ambulance, registered under Haldibari Sewa Samaj, a charity, in Jhapa, was on its way to Biratnagar from Sangurigadhi of Dhankuta. 

Ambulance driver Jayadev Chel, aged 48, from ward 8 of Biratnagar Metropolitan City, has been detained for investigation.

 The contraband was hidden inside the vehicle in small plastic packages of one kilogramme each. Detailed investigation is underway into the incident, said police.