(Source: Reuters) More than 200 people, including passengers and crew have been rescued from a Lithuanian ferry Lisco Gloria which was ablaze after an explosion in Baltic sea, officials said on Saturday. The explosion happened at about midnight on the upper deck of the ferry and caused fire on the ship. At least 20 people are slightly injured while three serious injured people were sent to hospital by helicopter, police said. Six ships joined in the rescue work immediately after the explosion as the ship was on a major shipping route near German island Fehmarn. police said. The people rescued have been sent back to the city of Kiel at about 6 a.m. local time. "People were lucky because it all happened on a major shipping route, that's why the other vessels were quickly on hand to rescue people," said Ulrike Windhoevel, the spokeswoman for Germany's Central Command for Maritime Emergencies in Cuxhaven. The reason for the explosion was still not clear, but current investigation showed that it was caused by a technical problem, police said. The ship was still on fire as the firefighters worried too much water would sink the ship. Windhoevel said, "firefighters were still spraying water on the ship's exterior to cool it down instead of putting out the blaze on the ship, because at some point it would sink because of all the water in it." Lisco Gloria was scheduled to leave Kiel at around 10 p.m. on Friday and was heading to Klaipeda, Lithuania, a journey which takes 21 hours.