BANGOR – FBI officials confirmed Friday that letters allegedly containing anthrax sent to about 200 abortion clinics – including the Mabel Wadsworth Women’s Health Center in Bangor – thus far appear to be hoaxes.

FBI spokeswoman Gail Marcinkeiwicz said Friday from her Boston office that while testing was not complete on the Maine letters, nearly identical letters received Thursday at three Massachusetts family planning centers tested negative for anthrax.

Maine State Environmental Health and Testing Laboratory officials on Friday said initial tests on the substance found at the Bangor clinic did not find any spores that could indicate an airborne form of anthrax. Health officials stressed further tests were needed to confirm that the granular substance was not anthrax.

The second round of tests is expected to be completed this weekend, one state health official said.

Ruth Lockhart, the Wadsworth center’s executive director, called the initial tests “very assuring,” adding that the Harlow Street center would remain open and continue to provide services.

“There’s no hysteria. It’s business as usual,” Lockhart said Friday afternoon. “Frankly, we expected it to be a hoax.”

The Bangor clinic was one of about 200 clinics and advocacy organizations – including an Augusta family planning center – that received letters Thursday delivered in Federal Express envelopes. Envelopes that were opened contained white powder and letters signed by “the Army of God.”

For two decades, a clandestine anti-abortion group calling itself the Army of God has carried out attacks on abortion providers and clinics, including bombings and sniper attacks.

Thursday’s mailings marked the second such wave of threats – more than 250 abortion clinics received similar letters last month. Thus far, none of the powder sent to the clinics has tested positive for anthrax.

In Bangor, Lockhart said the center’s staff immediately identified the cardboard FedEx envelope as suspicious based on its return address of the National Abortion Federation, a Washington, D.C., organization to which the center belongs. Lockhart said the agency wasn’t expecting anything from the federation, which does not routinely use FedEx for its mailings.

Staff opened the cardboard package and removed the white envelope inside, Lockhart said. Pursuant to the center’s protocols for handling suspicious mail, the letter was sprayed with a substance that allows staff to read its contents, according to Lockhart, who said she was able to read the phrases “you have ignored” and “real anthrax” through the unopened envelope.

Those who sent the letters somehow obtained the account numbers of Planned Parenthood Federation of America and the National Abortion Federation to pay for the mailings, according to officials of both organizations. They said packages have been tracked to at least three drop-off locations in Virginia and Philadelphia.

Most of the letters were received in states along the East Coast. Some also were reported in Detroit.

The Associated Press contributed to this report.