I think you are thinking of the accident in Goiânia (Brazil) in 1987, but this article is actually about the accident in Ciudad Juárez (Mexico) in 1983.

There have been quite a few accidents involving radiation sources from disused radiotherapy machines, see https://en.wikipedia.org/wiki/List_of_civilian_radiation_acc... . In particular, there was an incident in Taiwan in 1982 which seems extremely similar to the one described in this article, it also involved a Cobolt-60 source contaminating recycled steel.