Britain's Civil Aviation Authority says a huge increase in people carrying devices powered by lithium batteries onto aircraft poses a growing fire risk. A recent estimate said an aircraft carrying 100 passengers could have 500 lithium batteries onboard inside laptops, cameras, e-readers, tablet computers and other mobile devices, the BBC reported Tuesday. The CAA has been working with the U.S. Federal Aviation Administration to inform aviation professionals and the public how best to pack batteries safely and what to do if they happen to smolder or even catch fire. Geoff Leach, manager of the CAA's Dangerous Goods Office, told the BBC batteries bought from reputable retailers are regulated and safe if packed in a bag properly -- but cheap, copycat batteries bought from dubious sources online could develop a fault with dramatic consequences. Lithium batteries can contain enough energy to power mobile devices for hours, a potential problem if that energy is suddenly released through being shorted out or other malfunction, experts say. A number of airlines have begun training flight attendants and other staff how to deal with lithium battery fires, the BBC reported.