US Top Stories from Associated Press (AP)

Michigan Sen. Carl Levin said tests on suspicious letter sent to one of his state offices show no signs it was contaminated with poison. "I have been advised by the FBI that preliminary testing by the Michigan Department of Community Health, Micro-Biology Laboratory in Lansing showed negative results," the Democratic lawmaker said in a statement Thursday.

U.S. and international forces in Southwest Afghanistan are shifting their training of Afghan troops from general combat know-how to specialized skills, a Marine general who recently led troops in the region said Wednesday.

Amid confusion about an arrest, multiple news sources are reporting that a suspect has been identified in the Boston Marathon bombing investigation, based on surveillance footage from a Lord and Taylor department store and TV footage.

Police are investigating how the body of a dead baby that tumbled out of a pile of dirty Minnesota hospital laundry ever wound up in the sheets in the first place. A worker at Crothall Laundry Services was preparing the sheets for wash when the baby's body, outfitted with diaper and hospital tag, tumbled forth, The Associated Press reported.

The lawmaker behind a controversial cybersecurity bill found himself the focus of a Twitter campaign Wednesday, as the House girded for a debate on a proposed law to immunize companies that share cybersecurity information with the U.S. government.

A judge approved a $700,000 settlement between McDonald's and members of the Michigan Muslim community who claimed that a Detroit-area restaurant served food falsely advertised as compliant with Shariah law.

One of the world's leading experts on counterterrorism told an Australian paper Wednesday that Monday's Boston Marathon bombings have the markings of right-wing domestic terrorists, not jihadists.

With the nation on edge from deadly terrorist bombings in Boston and suspicious letters mailed to Washington officials, the White House said Wednesday it's premature to speculate that America is under attack. "Before we speculate, before we make connections that we don't know exist, as the FBI has said, we need to get the facts," said White House spokesman Jay Carney. "First things first."

Capitol Hill authorities are questioning a suspect who had suspicious letters in his backpack, Nebraska Sen. Ben Nelson said Wednesday. "Police are questioning a man who had numerous letters in a backpack. Thankfully, the safeguards authorities put in place since 9-11 are working to protect people," the senator said in a statement early Wednesday afternoon.

VIENNA, Austria (AP) , Technicians upgrading Iran's main uranium enrichment facility have tripled their installations of high-tech machines that could be used in a nuclear weapons program to more than 600 in the past three months, diplomats said Wednesday.

LOS ANGELES (AP) , Less than three months after the Roman Catholic Archdiocese of Los Angeles released the files of priests accused of sex abuse, attorneys for victims are back in court seeking similar records kept by more than a dozen religious orders.

The Pentagon is reconsidering a reduction in the number of its generals and flag officers as its active duty ranks decrease by 100,000 troops over the next five years, the chairman of the Joint Chiefs of Staff said Tuesday.

AUSTIN, Texas (AP) , A multimillion-dollar horse racing and breeding operation run from an Oklahoma ranch was actually a front for a notorious Mexican cartel to launder millions of dollars in drug money, prosecutors alleged Tuesday at the beginning of a trial for five defendants charged in the scheme.

The Pentagon will decide in the next two or three weeks whether it will require its 800,000 civilian workers to take unpaid leave this year, Defense Secretary Chuck Hagel told Congress on Tuesday.

The bombs that struck the Boston Marathon with such lethal force were fashioned from large pressure-cookers packed with nails and ball-bearings and hidden in black duffel bags on the ground, according to a U.S. official briefed on the investigation.