Belgian health authorities have warned citizens to stop using millions of cloth facemasks distributed by the federal government last year to fight the coronavirus pandemic.

A letter from health minister Frank Vandenbroucke, made public by the CSS national health council, says masks made in Asia by the Luxembourg firm Avrox may contain toxic materials.

In June last year, Belgium's central government procured 15 million Avrox masks and made them available free via private pharmacies to help protect its 11.5 million people.

But local communes were distributing masks directly to households and many private enterprises were selling them, reportedly meaning only a third of the federal models were used.

Now, following complaints from rival Belgian manufacturers, the CSS is investigating whether the masks are contaminated with toxic nanoparticles of silver and with titanium dioxide.

The Luxembourg firm insists that it followed all appropriate safety protocols, but Belgian authorities are recommending the masks be avoided while the probe continues.

mad/dc/tgb