(This July 16 story corrects, in the last paragraph, to show that London Concrete does not supply the Silvertown project after Extinction Rebellion corrects press release.)

LONDON (Reuters) - Climate activists from Extinction Rebellion on Tuesday disrupted London Concrete, the British capital’s biggest supplier of ready-mixed concrete.

Activists blocked entrances to the site. The group said it would disrupt the site for the day in an attempt to halt the expansion of the works.

“Concrete has a huge environmental impact,” said Eleanor McAree, 25, from Extinction Rebellion.

“Air pollution is already at dangerous levels and is affecting the health of children and adults in the area.”

London Concrete is a unit of Franco-Swiss group LafargeHolcim. Extinction Rebellion initially said the company supplies a major road tunnel project under the River Thames known as the Silvertown Tunnel, but later corrected that statement to say the company does not.