SPRINGFIELD, Ore. - An envelope containing a suspicious substance and a letter claiming the material was anthrax caused a lockdown that left as many as 1,000 employees stranded inside their office for four hours May 20.

Officials are now 99 percent sure the substance is sugar. Tests will be conducted May 21 at a lab in Salem to confirm the preliminary finding.

The scare started when an employee in Symantec Corp.'s complaint department opened an envelope containing a white granular material and a letter.

"There's a letter in there and it says anybody who has been exposed to this now has anthrax," said Brian Parmelee, the Springfield deputy fire marshall.

Although only one person opened the letter, 30 were in the vicinity. Up to 1,000 people were in the building at the time.

The company locked down the facility with employees directed not to enter or leave the building, according to Cris Paden with the company's corporate communications department in California. The company opened an on-site cafeteria to feed employees.

The original call for help came in around 3:25 p.m. about a supsicious substance found in a letter. Hazardous materials crews arrived on scene and suited up and entered the building at about 5:20 p.m.

The hazmat crews brought the material out to a trailer for testing. After about an hour, the verdict was in: sugar, not anthrax.

Employees were released in time to cast ballots in Oregon's May 20 primary. A ballot box was brought to the scene to help last-minute voters who were trapped in the building to cast their ballots.

The FBI is investigating where the letter came from.