Nobody expects to get a letter from a member of Congress that ends with an expletive.

But that's what happened when Rep. Jo Ann Emerson, R-Mo., recently corresponded with a resident of her southeast Missouri district.

The letter ended with a profane, seven-letter insult beginning with the letter a — "i think you're an. ..."

Emerson says she can't explain how the offensive language made it into the letter, which otherwise reads like a typical response to a citizen's question about last year's testimony of oil executives before the Senate Commerce Committee.

"There is no excuse for this inappropriate letter having been sent, and every apology has been made to the individual who received it," Emerson said in a statement to The Associated Press.

"We cannot determine whether the addition to the letter was made by someone within the office or by someone with access to the office, but it is on my letterhead and the responsibility for it lies with me. A valuable lesson has been learned and new procedures will be adopted as a result."

Spokesman Jeff Connor said the measures include locking down all computer workstations when they are not being used, increasing the editing of outgoing mail and reviewing policies on who has access to the office.

"No one has been disciplined at this time because we are not yet able to identify the person responsible," Connor said.

The man who received the letter, Bill Jones, of Centerville, Mo., declined to comment when reached by phone at his home Wednesday.

A copy of the letter had made its way to the Missouri Democratic Party, which faxed it to the AP.

Connor said that Emerson personally signed the letter, dated Feb. 15. She included a handwritten personal message at the bottom: "PS - please forgive the delay in responding."