La Paz -Some 249 mobile drug production laboratories and two tons of cocaine have been seized in a major enforcement operation in eastern Bolivia, resulting in around 20 arrests, officials said on Friday.

A vast pile of coca leaves and four clandestine airstrips, likely used by planes transporting the drugs elsewhere, were also discovered, said Colonel Gonzalo Quezada, national director of the country's drug enforcement police.

The operation took place between Tuesday and Thursday, said Bolivian Interior Minister Carlos Romero, who hailed it as a “very important blow” against the country's drug traffickers.

The discoveries were made in the villages of San German and Nuevo Horizonte, about 40 kilometers (35 miles) from Santa Cruz de la Sierra, which is 900 kilometers from La Paz, with police saying at least 20 people had been arrested.

Bolivian law on coca and controlled substances allow as much as 12,000 hectares of land in approved locations to be used to produce coca for legal purposes, however the country is the world's third-largest source of cocaine.