A mysterious substance that leaked onto a pallet of FedEx packages at the Ukiah Post Office on Thursday sent three postal workers to the hospital for evaluation, local fire officials said.

A hazardous materials team that spent the day at the South Orchard Avenue post office determined that the substance was a chlorinated hydrocarbon, a chemical used in pesticides and solvents, but was unable to find the source, Ukiah Valley Fire Capt. John Strangio said.

Fire personnel were notified of the leak at 9:30 a.m. when a postal worker handling some packages dropped off by FedEx for delivery noticed her gloves were deteriorating and felt a burning sensation on her hands, Strangio said.

Some of the oily-looking substance also dripped on the floor was was stripping off the wax, he said.

Two other workers in the vicinity experienced shortness of breath, as well.

The Redwood Empire Hazardous Incident Team assembled, and a mobile lab was brought in, while the wet packages were brought out to the loading dock of the post office for inspection.

As much as a half gallon of liquid appeared to have spilled, Strangio said.

Unsure what chemical they were dealing with, hazardous materials personnel donned fully encapsulated suits, cordoned off the area and took samples for testing, but determined there was no additional threat to those in the vicinity, Strangio said.

The three workers taken to the local hospital returned to work shortly thereafter, and business went on as usual in the public side of the post office, he said.