SIMI VALLEY (CBSLA.com) — After seeing many children in their community be diagnosed and treated for rare childhood cancers, a group of Simi Valley mothers is pushing for closer scrutiny of the 2,800-acre Santa Susana Field Laboratory – the site of a partial nuclear meltdown 56 years ago that the mothers believe to be causing an unusually high number of childhood cancer cases in the area.

The site, which was acquired by Boeing in 1996, was used over the course of 50 years to test rocket engines, nuclear reactors and liquid metals. There was a partial nuclear reactor meltdown in 1959 on the site that released an unknown amount of radioactive substances into the ground and atmosphere.

The site has been the topic of heated debate in recent years – including who should pay for the cleanup, how much can be done to remediate the environmental damage and what the ongoing health risks are for residents.

A 2007 study found that people living within two miles of the site had 60 percent higher incidences of certain cancers.

The cleanup was supposed to start in 2010 but has been tied up in lawsuits and bureaucratic delays, and still has yet to begin.

Now, a group of Simi Valley mothers who live near the site are calling attention to a rash of recent childhood cancer diagnoses in their community and demanding to know the extent of the risks they and their children face.

“0.003 percent is the national average for childhood cancers,” said one of the mothers, Melissa Bumstead. “I can name 10 children off the top of my head [who have been diagnosed with cancer] who live within 3 to 5 miles of my house.”

Ten mothers were set to participate in a town hall meeting Tuesday night to discuss their concerns.