The FBI wants to discover who sent an envelope containing an unknown white powder to the company on whose property a massive sinkhole opened, causing contaminated water and fertilizer to flow into Florida's main drinking water aquifer.

The FBI said Saturday it testing the powder delivered Friday to Mosaic Corp.'s Tampa area headquarters. The powder is being tested to see if it is dangerous.

So far, more than 200 million gallons of tainted water from the central Florida fertilizer plant owned by Mosaic has drained from a waste heap through a 45-foot-wide hole down into the Floridan aquifer, which provides water to millions in the state.

The company says it has seen contamination at a recovery well within a quarter-mile of the sinkhole, but has not seen contamination further away.

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