BERLIN, Germany (AP) -- Federal prosecutors began an investigation Tuesday after a suitcase and another piece of luggage with explosive material were found on a train and in a railway station in western Germany.

The first case, which was discovered Monday on a regional train and handed over to authorities at the Dortmund's central station, contained a propane gas tank, a detonator, batteries and three bottles of gasoline, prosecutors said.

An examination of the materials determined that they were potentially explosive, but authorities could not say why they did not explode or if they were intended to do so, Dortmund prosecutor Henner Kruse told The Associated Press.

The second piece of luggage, which was also found Monday in the main station in Koblenz, Germany, also contained a propane gas tank, prosecutors said.

Federal prosecutors took over both cases and launched an investigation into possible terrorist activities, the office of Prosecutor Monika Harms said in a statement. Police are searching for possible suspects.

According to ARD television, the luggage found in Koblenz also held a detonator and batteries and appeared to be similar to the explosives found in the Dortmund suitcase. Prosecutors could not immediately confirm the report.

Both pieces of luggage and their contents were being examined in an attempt to determine how they were linked and whether they were intended to be crude bombs, or whether they were explosive materials intended for other uses, prosecutors said.

In 2003, a suitcase containing a fully functional bomb with a propane gas tank was found on a platform in Dresden's central station during a busy holiday weekend. An engineer was tried and found guilty of planting the explosives and sentenced to 12 years in prison.