Police in South Africa have arrested five suspects, including three Mexicans, after uncovering a multi-million dollar crystal meth lab on a remote farm.

Officers raided the lab, in the northern town of Groblersdal, after getting tipped off about "suspicious activities", a statement from an elite police unit known as the Hawks said.

It added that the lab was operating on an industrial scale, producing the highly addictive drug for both local and international markets.

South Africa is one of the largest meth markets in the world and a transit location for illicit drugs, according to the United Nations Office on Drugs and Crime.

On Tuesday, four men - two South Africans and two Mexicans - appeared in court in Groblersdal in connection with the case but were not asked to enter a plea. Their next hearing will be on 1 August.

Gonzales Jorge, aged 51, Gutierrez Lopes, 43, Simphiwe Khumalo, 35, and Frederick Botha, 67, were arrested following a search of the farm last Friday that found crystal meth with an estimated street value of 2bn rand (approximately £84m; $108m).

Officers also found chemicals used to manufacture the drug, such as acetone.

The owner of the farm was among those arrested, news agency AFP reported the police as saying.

An additional Mexican suspect - Ruben Vidal Rodriguez - was later arrested on charges of manufacturing, dealing and possession of illicit drugs.

Mr Rodriguez appeared separately in court on Tuesday. He was also not asked to enter a plea and his case will continue on Wednesday.

"What makes this different from other [seizures] is the involvement of Mexican citizens," Katlego Mogale, national spokesperson for the Hawks, was quoted by AFP as saying.

"It means that our task has just become very difficult."

Since the beginning of this year, the Hawks have uncovered 10 drug labs and made 34 arrests.

South Africa's geography and porous borders made it an appealing transit location for drugs destined for Asia, North American and western Europe, the United Nations Office on Drugs and Crime said in a report last year.