As Polish river levels fall to record lows amid a prolonged drought, the material remains of Poland's tortured 20th-century history are coming to light on newly exposed riverbeds, with Jewish tombstones and the human remains of Soviet fighter pilots and their plane being found in recent days.

Those discoveries follow that of stone fragments from the early 20th-century Poniatowski Bridge across the Vistula River in Warsaw which the Germans blew up in 1944 as they crushed the Warsaw Uprising.

"The Vistula River is hiding no end of secrets. They are everywhere," said Jonny Daniels, the head of Jewish foundation "From the Depths," who waded into a shallow area of the Vistula on Tuesday, picking up fragments of stones with Hebrew lettering.

For the most part, officials knew that archaeological remnants remained hidden under wild and murky waters of the Vistula River or its tributaries. But it was simply impossible to carry out searches for them until now. Amid a prolonged drought, the Vistula, which flows 651 miles from the Beskidy Mountains to the Baltic Sea, is at its lowest level since measurements started in the late 18th century -- leading explorers and fortune-hunters to comb riverbanks across the country.

On Sunday, explorers found the remnant of the Soviet fighter-bomber plane in the Bzura River, a tributary of the Vistula, near the village of Kamion in central Poland. The pieces have been moved to a museum in nearby Wyszogrod for examination, with more recovery work planned for Saturday.

The head of the museum, Zdzislaw Leszczynski, told The Associated Press that parts of Soviet uniforms, a parachute, a sheepskin coat collar, parts of boots, a pilot's personal TT pistol and radio equipment were found, along with a lot of heavy ammunition. The inscriptions on the control panel and on the radio equipment are in Cyrillic.

The uncovered remnants are part of the larger story of a devastating war that played out across Poland from 1939-1945: a German invasion from the west, a Soviet invasion from the east, the murder of Jews across occupied Poland and fighting between the Soviets and Germans after Adolf Hitler turned on former ally Josef Stalin.

Leszczynski said that witnesses had described the plane being hit while flying low in January 1945 and crashing down through the thick ice and into the river. At that time in the area, the German army was retreating toward Berlin before the Red Army's advance.

"Until now, the water level did not allow for the search and there was no one willing to enter this swamp," he said.

Russian Embassy spokeswoman Valeria Perzhinskaya said she considers the discovery important and believes the crew could be identified by the numbers on the wreckage and could be properly buried. About 600,000 Soviet troops were killed fighting the German army on Polish territory.

The Jewish tombstones that were found in Warsaw are believed to come from the Brodno cemetery in Warsaw's Praga district. Once the resting place of 300,000 Jews, only 3,000 tombstones remain there today; the rest were removed during and after the war and used as building materials and to reinforce the river's banks.

Two weeks ago, a man walking along the river in Warsaw came across fragments of the tombstones with Hebrew lettering and took Daniels there on Tuesday. In the meantime, some had already been removed, though a few fragments were still lying on the riverbed. Now Daniels hopes to take students there to do a more thorough search and return anything he can find to the cemetery.

"Jewish history is buried in the Vistula," he said.