FORT KENT, Maine — Investigators have determined that a suspicious powder mailed with a letter to Fort Kent Elementary School on Tuesday was flour, the town’s police chief said Friday.

Chief Kenneth Michaud said he was told that testing completed on Thursday in Augusta had ruled out chemicals and determined that it was the common cooking ingredient.

The powder came in an envelope with a letter and had a Rowlette, Texas, postmark.

Tim Doak, superintendent of AOS 95, said the letter was opened in the principal’s office around noon on Tuesday, March 6. The secretary opened it and found the powder and a letter that “said some derogatory things about the FBI,” Doak said.

School officials immediately placed the envelope into a sealed zip-close bag, as protocol dictates. They then called police, who arrived a short time later.

The school was not evacuated.

FBI agents from Waterville drove up to examine the contents of the envelope.

Schools across the nation, including in Texas, Massachusetts and Rhode Island, have received similar envelopes with powder in them since Monday, according to The Associated Press. The contents have turned out to be cornstarch in several cases.