It could also be a faulty jumper wire. I once had a jumper starting to smolder in a cirquit with less than 500mA draw and as I janked it out of the breadboard, the wire broke in the connector. As I examined it, it looked like 1-2 threads was scorched and the rest looked like they had been broken during manufacturing of the wire (or due to wrong handling by me). The threads which carried the current must have been quite hot, causing the connector to melt 