Archaeologists say the mass grave containing horses could be related to the Eighty-year War, between 1568 and 1648.
Research has shown the grave dates from the 16th or 17th century.
Archaeologists believe the horses may have been slain during battle in the so-called Eighty-year War (1568-1648), or the French siege of Maastricht in 1673 by the Sun King, Louis XIV.
The tomb was unearthed several weeks ago during archaeological research commissioned and funded by the Consortium Grensmaas, an agency responsible for river protection works and gravel extraction.
Archaeologist Angela Simons, who works for Hazenberg Archaeology, which is co-ordinating the excavations on behalf of the consortium, said no tack had so far been found with the horses.
"The horses were piled in a ditch," she said.
The trench measured about 40 metres but may not have originally been dug as a grave, but as a fortification.
"We have nearly complete skeletons uncovered. We also found horse shoes."
Simons does not exclude the possibility of a link between the burial of the horses and the discovery of remains of French soldiers several years ago near the riverbank at Borgharen, not far from the current location of the horses' grave.
The dead soldiers were identified as French through the buttons found on their uniforms.
The horse remains will be investigated further and preserved.
Archaeo-zoologist Jessica Grimm, of the organisation Archeodienst, described the grave's discovery as unprecedented in Western Europe.
The age of the remains was established by measuring the radioactive decay of carbon in the skeletons.
The Netherlands National Office for Cultural Heritage was also closely involved in the archaeological investigations.
The public was given the opportunity to view the remains on Thursday (Netherlands time).