Environmental campaigners told a High Court judge today that an Olympic basketball training facility was being built on parkland filled with "lead and asbestos".
They said the facility in Waltham Forest, north London, was being put up in an area "landfilled" after the Second World War and workers were disturbing "contaminated" earth.
Demonstrators raised concerns as Mr Justice Arnold - who has said he has tickets for an Olympic basketball game - renewed an order "restraining" them from engaging in "unlawful activity" at the site.
The judge granted the injunction on April 4 after lawyers representing the Olympic Delivery Authority (ODA) - a public body responsible for building Games venues - said protesters were stopping workers getting to the site at Leyton Marsh, which is part of a regional park.
He renewed it at a High Court hearing in London today after hearing arguments from the ODA and protesters.
The judge was a told that the ODA had licensed the site from park owners. Planners had given permission on the basis that the facility would be demolished and land restored to its previous condition after the Games.
He said he had to balance the ODA's rights under that agreement and demonstrators' rights to free speech and assembly.
"The injunction doesn't prevent lawful or peaceful protest," said Mr Justice Arnold. "The court's function is to uphold the law."
He added: "It seems to me it is necessary and appropriate to grant the relief sought by the ODA."
The judge said the injunction would remain until after the Games or a trial of issues in dispute or further court order.
A number of protesters outlined their concerns to the judge at a two-hour hearing today.
One said the area had been used as a landfill site after the Second World War and "contaminated land" was "being disturbed".
Another, Daniel Ashman, said the area was "full of lead and asbestos".
Demonstrators said the parkland was "sacred" to locals as a "place to relax and take refuge from the noisy urban environment".
Protester Simon Moore told the judge: "It is priceless. It serves an essential human need that no building could."
Demonstrators said they were not opposed the Olympics but to development.
They complained that not enough local people had been consulted about plans for the facility.
Mr Justice Arnold praised the demonstrators' clarity and courtesy and said they had "made their points well".
Earlier this month, demonstrators were evicted from the site after separate legal moves by parkland owners.
A High Court official granted a possession order to the Lee Valley Regional Park Authority.
The official, Master Matthew Marsh, made the order after being told that the protesters had set up tents, collected wood and made fires in breach of park byelaws.
Lawyers representing the ODA told the judge today that four people had been arrested when the site was cleared following Master Marsh's order.
They said the continuation of the injunction was necessary because there was a "serious risk" that "unlawful activities" would continue.
The judge was told that protesters had moved to a nearby verge owned by a local authority after being evicted.