SANTA CRUZ, Calif. -- Health officials in Santa Cruz confirmed Tuesday that high levels of arsenic, copper and chromium have been found at Twin Lakes Beach.

Toxic levels of the substances were found at two fire ring sites.

At one site, tests showed levels about 70,000 parts per million. At the other site, the test measured 20,000 parts per million.

Arsenic is considered toxic at just 500 parts per million.

The high levels of arsenic were first discovered by the citizens group Friends of the Harbor and confirmed by tests conducted by the Monterey Bay Regional Air Pollution Control District.

It's believed that the burning of pressure-treated wood, which is injected with a the chemical mixture chromated copper arsenate -- CCA -- is the cause of the high levels.

The state Parks Department will ultimately decide how to deal with the problem. For now, officials said they're hoping to educate people about the hazards of using pressure-treated wood.

"What we're hoping is that with public cooperation ... if people don't burn these types of materials ... that we can continue to allow this kind of activity that's been enjoyed for decades along these beaches," Parks Department spokesman Dave Vincent said.

Pressure-treated wood is being phased out, but retailers are allowed to sell off remaining supplies.