>> we're in bukavu, the capital of south kivu to meet with abbas kayonga. abbas heads the the anti-fraud division of the ministry of mines here. when we told him we'd heard minerals had been tagged and sold illegally in nyabibwe, he said the site is currently under investigation. >> what can you tell us about incidents of fraud in numbi and nyabibwe? >> so you're saying the amount that's produced in nyabibwe is not very high, but the amount that is exported is very high. >> abbas and his agents track minerals from uncertified mines that arrive in the city. he told us that in the last 7 months they've intercepted 52 tons of illegal tin. he took us to a boat landing along lake kivu, one of the major conduits for mineral smuggling here. >> and how do your agents find out about this? >> and it takes place in little boats like this? >> are most of the minerals that are smuggled across, are they tagged or untagged? >> untagged. >> and where are they going? what's the no 1 destination? >> back in goma we tracked down a government whistleblower who asked to remain a