To the untrained eye, the human tide surging through the South African border town of Musina is just that: a mass of people leaving behind Zimbabwe's collapsed economy to seek job opportunities and a better life, or refuge in a neighbouring country.
Sebelo Sibanda, of Lawyers for Human Rights in Musina, is a more acute observer; he sees changes taking place in a migration that is believed to number between one million and more than three million people.
"A trend started in the last two or three months, where you see more and more women coming in with groups of children - the children are too numerous and often too similar in age to be from one mother," he said.
The Zimbabwean migration, comprising asylum seekers fleeing political persecution, economic migrants from a shattered economy, traders, shoppers and unaccompanied minors, provides ample camouflage for human traffickers.
The border between South Africa and Zimbabwe is a fertile ground for criminal gangs. The "magumagumas" prey on migrants, robbing and raping them as they make their way to South Africa, while the "malaicha" arrange safe passage for migrants, but do not always keep to the contract.
Nde Ndifonka, the southern African spokesman for the International Organization for Migration, told IRIN: "The conditions are there. We believe there is a high incidence of human trafficking happening there [the South Africa-Zimbabwe border]".
Parents living in South Africa often pay a malaicha to bring children across the border, Sibanda said, and it was a "small step" to becoming a human trafficker.
Ndifonka said the malaicha were part of trafficking rings and targeted "specifically, vulnerable young children, as there is a demand for labour and sexual exploitation in South Africa".
In mid-April 2009, during a spot check, police found two unaccompanied minors - boys aged about four and five - in a car en route to Johannesburg. "The woman at first said they were her children, but when I interviewed the children separately they said they did not know who she was," Sibanda said.
Human trafficking is difficult to detect, as people are generally not aware they are being trafficked. We know it [human trafficking] is happening but cannot detect it
The unseen crime
"The woman then maintained that she was their mother's sister, but the children did not know who she was, but were told by her to call her 'aunty'. The woman then said she was taking them to meet their mother in Johannesburg, but the children said their mother was living in Cape Town."
The woman is expected to be charged with kidnapping or a lesser charge of smuggling, as South Africa has yet to adopt human trafficking legislation.
An international children's agency, which declined to be identified, fearing it might attract human traffickers to its offices, told IRIN it had begun trying to trace the children's relatives. The aid worker said people claiming to be the relatives or friends of parents had tried to lure children away from the shelter.
"Human trafficking is difficult to detect, as people are generally not aware they are being trafficked. We know it [human trafficking] is happening but cannot detect it," Jacob Matakanye, CEO of the Musina Legal Advice Centre, told IRIN.
"The only way to prevent trafficking is to educate people about it in the country of origin ... Zimbabwe is an ideal opportunity for traffickers, as it is next to South Africa [the continent's richest country]," he said.
The UN defines human trafficking as "The recruitment, transportation, transfer, harbouring or receipt of persons by means of threat or use of force or other forms of coercion, of abduction, of fraud, of deception, of the abuse of power or of a position of vulnerability, or of the giving of or receiving of payments or benefits to achieve the consent of a person having control over another person for the purpose of exploitation."
This article was produced by IRIN News while it was part of the United Nations Office for the Coordination of Humanitarian Affairs. Please send queries on copyright or liability to the UN. For more information: https://shop.un.org/rights-permissions