(Santa Ana-AP) -- Tracking the source of dangerously high levels of lead often found in Mexican candies sold in the United States requires going back to the source -- the fields where the chilies used in the candies are grown.

The Orange County Register reports the chilies are clean when they are harvested but often become tainted on the way to factories where the candies are manufactured.

Authorities who performed more than 15-hundred tests on Mexican candy in the U-S since 1993 have found high levels of lead in one out of every four samples.

Lead poisoning can cause irreversible brain and nerve damage and result in lowered intelligence and behavioral problems -- particularly in children.

State officials estimate that as many as 15 percent of California children who suffer lead poisoning have eaten Mexican candy.

Mexican officials are promising to investigate.