Toronto police say there is no threat to public safety after demonstrators dumped barrel containing an unknown white liquid in front of the main entrance to Queen’s Park.

Const. Victor Kwong said police were called at 10:17 a.m. to respond after callers reported that demonstrators dumped a barrel containing “a white foamy substance” onto the ground.

The demonstrators’ barrels have the website written on them.

A news release from demonstrators say they are demanding that the province address evidence of a large deposit of mercury upstream from Grassy Narrows First Nation north of Kenora. Residents of Grassy Narrows have reported suffering symptoms consistent with mercury poisoning for many years.

Toronto Fire Captain Stephan Powell said Hazmat and Police CRBNE response teams are at the scene. The Toronto Police bomb squad also responded to the scene. Powell said he has been told the substance appears to be a mix of corn starch, water and soluble paint.

But the liquid will still be sampled and tested.

A CTV camera operator saw six people being loaded into a police van.

Const. Craig Brister said six people have been arrested and charged with one count each of mischief.

He said the dump poses no threat to public safety. But the south lawn of Queen’s Park as well as the legislative building is closed to the public and will remain closed for some time.

Demonstrators said in a news release that they want the provincial and federal government to clean the watershed and area around Grassy Narrows First Nation, something Ontario Premier Kathleen Wynne has pledged to “resolve.”

Activist Syed Hussan said residents of Grassy Narrows have suffered from mercury contamination for as many as 40 years.

“Kathleen Wynne needs to commit to cleaning up the river system.”

Hussan would not say what was in the barrel that was dumped on Queen’s Park grounds.