SANTIAGO, Sept. 24 (Xinhua) -- Chile on Monday declared a health warning sparked by air pollution levels in the coastal towns of Quintero and Puchuncav, in central Valparaiso region.

Officials also ordered local polluting industries to suspend operations, following hundreds of cases of residents showing signs of intoxication from high concentrations of contaminants in the air.

The government is looking for a permanent solution to the crisis, which has been decades in the making, Environment Minister Carolina Schmidt told reporters.

"The government has taken every step to reduce such episodes in the area" but "you can't eliminate more than 50 years of pollution in one month," said Schmidt.

Officials are mulling tougher emissions standards for sulfur dioxide (SO2) by adopting international norms, a move environmentalists have been demanding for some time.

The alerts were issued after numerous students fell ill in recent weeks, forcing local authorities to suspend classes and launch emergency treatment centers.

On Monday, school children in the two towns were due to return to school after the government moved to call off a yellow-level alert, a decision locals and Chile's Medical College were against.

President Sebastian Pinera recently pledged to clean up communities contaminated "with arsenic" and other pollutants, including "carbon and hydrocarbon" runoff from area industrial plants.

"We have a strong presumption that arsenic could be the cause of the high incidence of cancer that affects many inhabitants in these two towns," said Pinera.?