I just heard about this, but apparently the government back in mid February forbade all fishing and swimming in Lake Kivu for an indeterminate period, saying that high levels of methane and carbon dioxide had caused several deaths by drowning. The fishermen are understandably miffed.
Lake Kivu is one of Africa's three "exploding lakes," along with the infamous killer lakes in Cameroon, that experience periodic lake overturns, where the compressed gas within the lake surfaces, poisoning the surrounding landscape.
I used to swim in Lake Kivu, back in the day, off the Peace Corps dock . It was said that bubbles of methane would occasionally rise to the surface, killing fishermen out casting their nets in the evenings. The pirogues would drift back to shore with no one on board, and days later the men's bodies would mysteriously wash up on shore. You can imagine the legends that ensued.
I've always heard that Kivu poses no Cameroon-style threat, that the likelihood of an actual sudden and violent overturn is vanishingly small--but this NBC piece from a couple of years ago says that a catastrophic event takes place in Kivu once a millenium. Given the millions of people who live nearby, I wish I could be confident that the international community is keeping an eye out on this. I learn from Wikipedia that a new effort is underway to tap the lake's vast reserves of methane, naturally, from the Rwandan side. And that "kivu" means lake in "Bantu language." But nothing on whether anyone's looking out for the three million people who live on its perimeter.
 I myself was not a PCV, but had lots of friends who were.