U.S. officials said Tuesday that another drone aircraft has mysteriously crashed, this time while on routine patrol around the small island nation of Seychelles, east of Africa.

It's the second U.S. drone to crash this month: less than two weeks ago a drone went down in Iran, where officials there paraded it around for cameras and demanded immediate compensation from the U.S. government for violating their airspace.

It's not known what caused either drone to crash, and in both cases officials have said it was likely due to mechanical failure.

The crash in Iran whipped up speculation of a possible cyber-attack, after an Iranian official claimed they brought the drone down by hacking into it and commandeering the controls. Unnamed intelligence officials who spoke to reporters said that Iranian hackers could have accomplished the feat with the help of hackers in China or Russia, but there's no proof of that yet.

There were also reports back in October of a mysterious virus that had infected America's drone fleet. Engineers said that it might just be common malware, but it kept coming back after they erased it from their systems.

The software contains a keylogger that may have been sending information to parts unknown over the Internet. Wired magazine noted that it had infected systems that handle both common information and classified materials.

There's no proof of any correlation between the virus and the crashed drones, and military officials aren't keen to elaborate.