A ferry in the Baltic Sea with 335 people on board is on fire after an explosion in the engine room

The military has sent a helicopter to the ferry and has two more on standby if needed, a spokesman for the Lithuanian air force told Reuters. The explosion was in the engine room, they said.

Alexei Kravchenko, a spokesperson for Lithuania's Federal Agency for Maritime and River Transport, told Russian news site Sputnik that are no casualties.

The ferry sent out a distress call at 10.45 a.m. GMT  (6.45 a.m. EDT), Reuters reported. It was travelling to the Lithuanian port town of Klaipeda from Kiel, Germany.

The ferry is off the coast the Russian city of Kaliningrad. A Greek news outlet, Sigma Live, posted what appears to be an image of the ferry.

Russian rescuers have also been mobilized for the rescue operation, Russian state news outlet RT reported.