There have been some anomalies that could be considered magnetic monopoles found in weird materials called "spin ice."
First off, when you normally think of magnetic monopoles, you think of a particle that carries a net magnetic orientation (like only South or only North), in the same way that an electron has a negative electrical charge. A particle like this has never been found in all the years people have tried.
The researchers tested and found a different concept of magnetic monopole that did show an overall single magnetic charge. A spin ice is a material that for physicists' purposes can't become a true solid. The "monopole" was the result of the particles in the spin ice exhibiting "split dipoles" a phase change under certain conditions. Keep in mind, all magnets until this observation were always full dipoles (with both North and South). The idea that a dipole may split brings about the possible discovery of a monopole.
Here's a paper from the prominent journal Nature that gives some specifics.
Don't worry, though. Unless you work with spin ice, it looks like Maxwell's equations still hold!