HARRISBURG - When an envelope addressed to Gov. Rendell began leaking a white powdery substance yesterday afternoon, mailroom staffer Wayne Boulware did not panic. He calmly put it down, picked up the phone, and called authorities.

As it turns out, the substance was most likely infant cereal, according to state officials. But the incident caused enough concern that the governor's mailroom was evacuated for almost an hour as FBI agents collected samples of the powder in their investigation.

Federal authorities believe the envelope sent to Rendell - postmarked in Texas - was part of a larger hoax in which similar envelopes have been sent to governors in 45 other states, as well as 15 U.S. embassies, in the last week.

In Harrisburg, no mailroom employees were hurt. The governor continued with his scheduled meetings as federal authorities locked down the mailroom from 2 to 2:45 p.m., Rendell spokesman Chuck Ardo said.

"His security detail was on the scene and didn't feel the need to evacuate him or limit his schedule," Ardo said.

Ardo said Boulware and other mailroom staffers had been warned to watch for correspondence from Texas. When Boulware spotted the envelope with the Texas postmark yesterday, he opened it gingerly - and when it began to drizzle the white substance, he immediately set it aside.

"He said he never got nervous," Ardo said. "He was remarkably unflustered by the incident."

The offices of State Rep. Dwight Evans (D., Phila.), which are across the hall from the mailroom, were locked down as a precaution.

"I think people were amused more than anything," said Johnna Pro, Evans' spokeswoman. "It was hard to take it seriously, even though it is a very serious matter."

Pennsylvania and Maryland yesterday became the 45th and 46th states to receive such envelopes, according to FBI Special Agent Mark White, a spokesman in the Dallas office, which is coordinating the investigation.

Only the governors of Arkansas, Kentucky, Massachusetts and Ohio have not received such envelopes.

The FBI believes the envelopes have all come from the same person. All had a postmark from the Dallas area and contained "similar written content," White said. He would not elaborate.

White also said the envelopes all had the same fake return address.

Lab tests on envelopes from other states found the contents to be corn starch or flour, he said. But in none of the cases was the substance harmful.

Last week, a 53-year-old Blair County man was charged with harassment and ethnic intimidation for allegedly sending a threatening e-mail message to Rendell.

"Dear Big Ed. I pray every night that a Christian or Arab puts a bullet through your corrupt jewish skull," wrote Vincent Lee Stone Jr. of Tyrone. He criticized the governor and warned: "Your smug demenor [sic] will not protect you, nor your smile."

Authorities do not believe there was any connection between the e-mail and the envelope.

Contact staff writer Angela Couloumbis at 717-787-5934 or acouloumbis@phillynews.com.