Residents of San Francisco's Treasure Island are seeking $2 billion in a class-action lawsuit and calling for the island's $6 billion redevelopment to halt until the land is free of contamination

The island, which sits in the bay between Oakland and San Francisco, was once used as a US Navy base starting in the 1940s.

Nuclear training operations resulted in radioactive elements seeping into the soil, and the Navy also used the ground as a waste dump to dispose of contaminants.

Since the 1990s, the Navy has been tasked with cleaning the island and delivering pollution-free parcels of land one by one to the city of San Francisco, which obtained the land in the 1990s to eventually build a grand neighborhood out of the man-made island. Over the next couple of decades, the formerly homeless and others in need of supportive housing would call the island home.

Now with the multi-billion-dollar redevelopment planned, which may or may not be paused as a result of the lawsuit, they'll be joined in the coming years by thousands of new residents.

In the decades since the Navy was tasked with the island's clean-up, there's been back-and-forth on whether or not the land is actually clear of contaminants.

At the time of a Reuters investigation in January 2019, Navy contractors during its cleanup had unearthed 1,289 low-level radioactive objects in the ground beneath the island neighborhood, some in areas it previously deemed to be clear of contaminants. But the Navy published a report in March 2019 stating that there was "no radiological health risk" posed to Treasure Island residents. Six months later though, the Navy disclosed that it had unearthed a chunk of low-level radioactive dirt the size of a basketball that had previously gone undetected, which it also claimed posed no real threat.

Lastly, a September 2019 report in the San Francisco Chronicle revealed that the island was so hazardous it was once considered to be labeled a Superfund site, a classification given to the most polluted areas in the US.

Residents claim that they've developed health problems since moving onto the island, which they say is because of exposure to the island's contamination.

When Business Insider met with a resident of 12 years, Trelease Miller, at her Treasure Island home in 2019, Miller said her daughter was one of the handfuls of children that had developed hair loss and puss-filled lumps since moving onto the island.

Former Treasure Island resident Kathryn Buckner told Business Insider's Aria Bendix that she has been diagnosed with melanoma since moving onto the island and had a tumor removed from her left arm in 2015. It is unclear if either Miller or Buckner is among the plaintiffs involved in the lawsuit.

The 2019 Reuters report also revealed that multiple residents had been taking their health problems, like cancer and children's hair loss, to the state for years. But no scientific evidence has been found that definitively proves the land has made residents sick.

A US Navy representative told Business Insider's Aria Bendix that the island is "safe for residents, employees, and visitors." State and federal agencies also maintain that the island is safe.

Read the full report regarding the lawsuit on The San Francisco Chronicle.