A Texas fertilizer factory exploded in a huge fireball Wednesday, flattening nearby homes and perhaps killing as many as several dozen people, with one official likening the blast to a "nuclear bomb." Fears were mounting in the small town of West, outside Waco, that a second fertilizer tank could erupt in flames, stoking anxiety in a nation already on edge after the nerve-jangling Boston marathon bombings, which left three dead.

Some 60 to 70 people were killed and hundreds were injured by an explosion at a fertilizer plant outside Waco, Texas, local media reported, citing the local emergency manager. The report could not be immediately verified by AFP, but KWTX television cited West Emergency Management Services Director George Smith as confirming the death toll. The explosion comes as the United States was on edge as it pieces through deadly explosions that hit the Boston marathon on Monday, followed by letters, apparently poisoned with ricin, sent to President Barack Obama and a US senator.

US President Barack Obama's gun control drive in the wake of the Newtown massacre suffered a major setback Wednesday when the Senate voted down expanded background checks on firearms buyers. The measure, which would have required background checks on sales at gun shows and on the Internet needed 60 votes for approval, but it fell well short, 54-46, as a handful of Democrats either facing tough re-election challenges in 2014 or from pro-gun states stood in opposition of the amendment.

The most significant US Senate debate on gun laws in 20 years starts Tuesday with the chamber introducing a bipartisan compromise on background checks, as both sides expect a razor-thin vote this week. The measure's two primary authors, Democrat Joe Manchin and Republican Pat Toomey, spent much of Monday scouring the 100-member chamber for last-minute support for the deal, which got a surprise boost when the second-largest US gun rights group came out in favor of it.