The FBI and Homeland Security are participating in the investigation into who made the anonymous threats at 11 gay bars, but are referring all questions to Seattle Police.  The police department will say little except that it takes the threats seriously.

Police patrols have increased in the Capitol Hill area where the bars are located.

The threats were made in typewritten letters received by the bars on Tuesday. The weekly newspaper The Stranger received a 12th letter saying it should be “prepared to announce the deaths of approximately 55 individuals.”

Despite the threats, business at the bars has shown little sign of slowing down, although many patrons say they are more vigilant. Tonight, an ad hoc group will hold a Capitol Hill Pub Crawl. The group on its Web site is urging gays and their supporters to attend.

The site also reminds people going to bars to look out for each other and “never leave your drink unattended or accept a drink from a stranger.”

Ricin is a poison found naturally in castor beans. It can be in the form of a powder, a mist, or a pellet, or it can be dissolved in water or weak acid.

If made into a partially purified material or refined into a terrorist or warfare agent, ricin could be used to expose people through the air, food or a liquid.

While law enforcement is tight lipped about the investigation, some people within the city’s LGBT community say they suspect the threats came from someone who is gay.

They cite a line in the threatening letters loosely taken from the poem “A Display of Mackerel” by openly gay writer Mark Doty. The poem was published in Doty’s book, Fire to Fire: New and Selected Poems, which won the 2008 National Book Award for Poetry.

“The targets won’t care much that they’ll be dead and nearly frozen, just as, presumably, they didn’t care that they were living,” the letters said.

Doty told The Seattle Times that he wrote the poem in 1994 as a meditation on the nature of the self and mortality after his partner died of AIDS.

Some, including Dan Savage, the editorial director of The Stranger, say the reference to the poem suggests the letters came from someone who is gay.

“It’s a gay self-hater,” Savage told The Times.

“Somebody who was seriously interested in killing a bunch of people at a gay bar wouldn’t announce the method of the attack in advance.”

The threats were made in letters received by the bars on Tuesday and have been turned over to police. Seattle weekly newspaper The Stranger received a 12th letter saying it should be “prepared to announce the deaths of approximately 55 individuals.”

Seattle police forensics investigators are examining the letters and the FBI and Homeland Security have been notified.

Ricin is a poison found naturally in castor beans. It can be in the form of a powder, a mist, or a pellet, or it can be dissolved in water or weak acid.

If made into a partially purified material or refined into a terrorist or warfare agent, ricin could be used to expose people through the air, food, or water.

In the 1940s, the U.S. military experimented with using ricin as a possible warfare agent. In some reports, ricin has possibly been used as a warfare agent in the 1980s in Iraq and more recently by terrorist organizations.

“We are actively investigating and coordinating with the FBI and other federal partners,” Seattle police said in a statement. “We encourage the community to be alert for suspicious activity and call that activity in to 911 immediately.”

The letters make no mention of a reason for targeting the gay bars and were not signed.

“I have in my possession approximately 67 grams of ricin with which I will indiscriminately target at least five of your clients,” the letters said. “I expect them to die painfully while in the hospital.”

Police said that if the sender is found he or she will face hate crime charges. Federal terrorism charges also are possible.