After the mysterious crash of a plane in the Baltic Sea, there is still no trace of the occupants.

According to the Latvian Sea Rescue Coordination Center, a wreck and debris were discovered in the sea during the night-time search operation.

However, no passengers had been found by Monday morning, said the head of the agency, Peteris Subbota, on Latvian television.

The wreck is now to be brought to the port city of Ventspils.

The private plane on the way from Spain to Cologne flew over the Baltic Sea and crashed into the sea off the coast of Latvia.

The Air Force confirmed the plane's crash on Twitter on Sunday evening.

Previously, all contact with the plane was broken off.

According to information available to the rescue service, there were four people on board, Subbota said.

According to the head of the Latvian sea rescue service, the search operation is currently taking place in an area six by six kilometers.

The Baltic Sea is about 60 meters deep at this point.

The fact that the exact place and time of the accident are known makes the search easier.

As the Swedish sea and air rescue center announced, Latvian authorities have taken over the management of the search.

They are therefore supported by emergency services from Estonia and Lithuania.

Many questions about the accident and its cause remained unanswered on Monday.

According to the Swedish broadcaster SVT, the flight safety expert Hans Kjäll suspects that there could have been a pressure drop in the cabin of the aircraft, after which the occupants had become unconscious.

The plane was flying at an altitude of about 11,000 meters, where the air pressure is low.

If there is a drop in pressure at such an altitude, you can expect to become unconscious, he said.

The aircraft was a Cessna 551, as reported by the Swedish newspaper "Dagens Nyheter".

The machine flew over the island of Rügen, entered Swedish airspace, flew south of Gotland and on towards the Gulf of Riga and then crashed into the sea.

Actually, the plane should have landed at Cologne-Bonn Airport in the early evening.

"Bild" reported that the machine reported pressure problems in the cabin after taking off from Jerez in southern Spain.

Accordingly, contact with the ground broke off just behind the Iberian Peninsula.

In the airspace over France, a squad from the French army took over, before a squad from Neuburg an der Donau and later from Rostock-Laage took off in German airspace.

A government representative told the Latvian news agency Leta that the rescue operation is currently in full swing.

Air force forces also wanted to take part in the operation, for which a Stena Line passenger ferry was also diverted.

The ferry should be ready for possible rescue operations.

The head of the Latvian Sea Rescue Coordination Center previously said on Latvian television that searches were being coordinated and the area was being combed.

Search helicopters from Lithuania and Sweden are also involved.

There is currently disagreement as to which jurisdiction the crash falls into.