A Mississippi man was arrested Wednesday, accused of sending letters to President Barack Obama and a senator that tested positive for poisonous ricin and set the nation's capital on edge a day after the Boston Marathon bombings.

Paul Kevin Curtis, 45, was arrested at his apartment near the Tennessee state line east of Memphis, said FBI Special Agent in Charge Daniel McMullen. It wasn't immediately known where he was being held.

Rescue workers searched rubble that witnesses compared to a warzone early Thursday for survivors of a fertilizer plant explosion in a small Texas town that killed as many as 15 people and injured more than 160 others. The blast left the factory a smoldering ruin and leveled buildings for blocks in every direction.

The explosion in downtown West, about 80 miles (130 kilometers) south of Dallas, shook the ground with the strength of a small earthquake and could be heard dozens of miles away. It sent flames shooting into the night sky and rained burning embers, shrapnel and debris down on shocked and frightened residents.

U.S. officials denied a suspect was under arrest Wednesday in the deadly Boston Marathon bombings.

A law enforcement official briefed on the investigation told The Associated Press earlier in the day that a suspect was in custody. But the FBI and the U.S. attorney's office in Boston said no arrests had been made.

Hundreds of women who received faulty breast implants are gathering in the south of France for the fraud trial of five executives accused of using cheap industrial silicone to fill tens of thousands of implants around the world.

Jean-Claude Mas, who founded and ran implant-maker Poly Implant Prothese, is among those on trial beginning Wednesday in the southern city of Marseille. The now-defunct company had claimed exports to more than 60 countries and was one of the world's leading implant makers.

Sheikh Salman bin Ibrahim Al Khalifa launched his campaign to head Asian football with plenty of talk about match fixing, grassroots football and more equitable spending of revenues.

But when it came to human rights in his divided nation of Bahrain, Sheikh Salman had little to say.

The Los Angeles Clippers trounced the Portland Trail Blazers 93-77 on Tuesday for their sixth straight victory, on a night that saw the Celtics-Indiana Pacers game in Boston canceled in the wake of Monday's deadly bombings at the Boston Marathon.

Caron Butler scored 18 of his 22 points in the third quarter, Blake Griffin added 16 points and DeAndre Jordan had 10 points and nine rebounds for the Pacific Division champion Clippers, who finished their home schedule with a 32-9 record.

From London to Sochi to Rio de Janeiro, the deadly bomb attacks on the Boston Marathon raised new concerns Tuesday over safety at major sports events around the world, including the Olympics and World Cup.

The twin bombings near the marathon finish line that killed three people and injured more than 170 people brought into sharp focus the security challenges facing next year's Winter Olympics in Sochi, Russia, the 2014 World Cup in Brazil and the 2016 Summer Games in Rio.

Wales will have two teams in next season's Premier League after Cardiff gained promotion to the lucrative top flight on Tuesday for the first time in 51 years.

Cardiff, which was playing in the fourth tier and suffering severe financial hardship only 11 years ago, guaranteed a top-two finish in the League Championship thanks to its 0-0 draw against Charlton.

An envelope addressed to a Republican senator tested positive Tuesday for ricin, a potentially fatal poison, congressional officials said, heightening concerns about terrorism a day after a bombing killed three and left more than 170 injured at the Boston Marathon.

One senator, Claire McCaskill of Missouri, said authorities have a suspect in the fast-moving ricin case, but she did not say if an arrest had been made. She added the letter was sent from an individual who frequently writes lawmakers.

The FBI's investigation into the bombings at the Boston Marathon was in full swing Tuesday, with authorities serving a warrant on a suburban Boston home and appealing for any private video, audio and still images of the blasts that killed three and wounded more than 170.

President Barack Obama said it was unclear whether the bombings were carried out by an international organization, domestic group or a "malevolent individual."