PORTLAND — Scientists are sounding a warning that the New England shellfish industry faces a potential threat of widespread red tide outbreaks this spring and summer.

Researchers say indicators are in place suggesting a significant regional bloom of the toxic algae that causes red tide.

The toxins are absorbed by shellfish, making them off limits to harvesting. The toxins don’t affect the shellfish themselves, but consuming mussels or clams affected by red tide can cause sickness and even death in humans.

Last summer, officials shut down nearly the entire Maine coast to clam digging because of an outbreak that officials said was the worst they could remember.