North Korea is very cautious about releasing information on stuff which happens in the country.
In April 2004, there was a massive train crash in North Korea, which left loads of people dead and injured.
It took 10 hours for the first reports of the crash to reach the UK.
Even after that, North Korea did not make a statement confirming what had happened.
Local media reports didn't mention the crash.
The press in the country is tightly controlled by the government.
People have to ask permission to travel around. It's hard for people to visit the country too.
Many people are poor and don't have the use of telephones, e-mail and other equipment.
It means information cannot get out or in to the country, so many secrets are kept.