UPDATED: Envelope Sent to Memorial School Contained Cornstarch; FBI Investigating

Updated: The white powder mailed in an envelope to was determined to be cornstarch, according to Milford police, and three other schools in New England also reportedly received similar mailings Tuesday.

Children at Memorial were kept in their classrooms after the investigation began about 11:45 a.m., but were allowed to eat lunch as normal in the basement cafeteria, school officials said. Dismissal was not affected by the incident.

The white material fell out of an envelope opened by a school secretary, said Milford Deputy Police Chief James Heron, triggering the investigation by state and local hazardous materials experts.

The envelope was addressed to the school, but not a particular person, and mailed from Dallas on March 2, according to Superintendent of Schools Robert Tremblay. The return address and delivery address were printed onto a sticker, affixed to the envelope. Three similar envelopes were delivered to schools in New England Tuesday, Tremblay said. The others were reportedly in Dedham, and at schools in Connecticut and Maine, he said.

on Tuesday afternoon reported a hazardous materials investigation at Dedham Middle School.

The FBI has contacted Milford police about the letters, Heron said.

Tremblay photographed the envelope and said he would share the image with the state Superintendents Association. He has already told all school secretaries in Milford to not open any envelopes that have the Dallas address.

Tremblay said the children at the school were unaware of the situation playing out in the front office, and the response of emergency personnel to the front of the school. Only the kindergarten classes have windows facing the street.

Because the envelope was opened in the front office, all of the people in it were told to stay in that room, Tremblay said. The personnel included the school's principal, Lisa Burns, who was in her office when the secretary opened the envelope.

The children and teachers simply stayed away from the office area, he said.

"School went on," Tremblay said. "From the kids' perspective, there was no change."

While this was happening inside, outside the school, a half-dozen parents waited for information about what was going on. Several said they had received a reverse-911 call from the school superintendent, informing them that a suspicious white powder had been found in an envelope in the principal's office.

David Engrassia, whose son is in the first grade, said he received the call on his cell phone, and then his wife called. "She was concerned," said Engrassia, who works as a school custodian in another district.

Engrassia was satisfied his son was safe, in his classroom, but said he wanted to pick him up on dismissal, in case he had been scared by the incident. "He's inquisitive," Engrassia said. "Just in case they release him [early], I want to be here."

Tremblay said he sent out an initial notification once he had some information, to all Milford parents, not just the Memorial Elementary parents. And then he said sent out an update when the field tests indicated the substance was harmless.

The initial information, while incomplete, is important because parents learn quickly that something is happening at the school. "My feeling is you keep families informed, otherwise, they presume it's worse than what it is."

As to why Memorial Elementary was targeted, among others in the New England region, Tremblay said he was perplexed. "Whether it was random, I don't know."