State College Medical Services, 477 E. Beaver Ave., was evacuated at 11:10 a.m. yesterday when an employee at the clinic opened a suspicious letter, State College Police Department said.

An employee for the clinic opened a letter yesterday morning, and upon opening it, white powder fell from the envelope, State College Police Officer Rick Ososkie said. A letter contained inside the envelope claimed that the powder was anthrax bacteria. The employee immediately called 911. Centre County Emergency Management Agency, State College Police Department and the FBI responded to the incident and the employees were taken to Centre County Hospital as a precaution.

The letter and its contents have been sent to a State Health laboratory for analysis, which is expected to take several days, police said.

The patients were later discharged, according to a hospital spokesperson, although they would not comment on what exactly they were treated for, and how many went to the hospital.

The 477 E. Beaver Ave. building remains open, although the clinic remains closed until results from the State Health laboratory come in.

The police urge anyone who receives a suspicious letter to remain calm, contain the letter in a plastic bag and call 911 to follow further instructions.

A similar letter was received in the Bellfonte area, a press release from the police department said.

Most of the letters are simply hoaxes, police said in a press release.

The FBI is conducting a criminal investigation with the assistance of the State College Police Department.