Researcher Wieger Wamelink inspects the plants grown on Mars and moon soil simulant in a research facility at the university in Wageningen, The Netherlands on May 6, 2016

Dutch scientists said Thursday crops of four vegetables and cereals grown on soil similar to that on Mars have been found safe to eat, amid plans for the first manned mission to the planet.

Abundant harvests of radishes, peas, rye and tomatoes all grown on the soil were found to contain "no dangerous levels" of heavy metals, said the team from Wageningen University in the Netherlands.

"These remarkable results are very promising," said senior ecologist Wieger Wamelink.

"We can actually eat the radishes, peas, rye and tomatoes, and I am very curious what they will taste like."

Future Mars settlers will have to take food supplies with them and then plant crops in order to survive.

So using soil developed by NASA to resemble that of the red planet, the university has been experimenting since 2013 and has managed to raise 10 crops.

But uncertainty remains about whether they would absorb the high levels of heavy metals such cadmium, copper and lead, present in Mars soil.

Further tests are now needed on the remaining six crops, including potatoes, in research which is being backed by a crowd-funding campaign.

NASA plans a manned trip to Mars within the next 10 to 15 years or so, and similar projects are also being pursued by US billionaire Elon Musk and the Dutch company Mars One, tentatively aiming to set up human colonies on the Red Planet.

The Mars One project has backed the Wageningen experiments and is currently undertaking a third selection to whittle down the remaining 100 candidates hoping to be among their astronauts to 40.

"It's important to test as many crops as possible, to make sure that settlers on Mars have access to a broad variety of different food sources," said Wamelink.