Summary:
French police are investigating a hostage situation in a post office near Paris in which the gunman took five people hostage before surrendering.

Full article:
Paris (CNN)A man with a handgun entered a post office outside of Paris early Friday afternoon before reportedly surrendering and releasing his hostages unharmed. The incident in Colombes, a community about 10 kilometers northwest of the French capital, began at about 12:45 p.m. (6:45 a.m. ET) and was over two hours later. The gunman might be mentally unstable, according to police in Colombes. Police said that they don't know yet whether the incident is related to terrorism. This is a hot topic in France after last week's deadly attacks. A Western intelligence source said there could be as many as 20 terrorist sleeper cells of between 120 and 180 people ready to strike in France, Germany, Belgium and the Netherlands. The gunman eventually surrendered and the hostages emerged with no injuries, according to France Bleu, which is part of the country's public broadcasting group. CNN's Greg Botelho and Elwyn Lopez contributed to this report.