In a statement issued to the news media, the UN Interim Force in Lebanon (UNIFIL) said it was informed by the Lebanese Armed Forces (LAF) that an IDF patrol had crossed the so-called Blue Line separating the two countries two days ago in the general area of Labouneh and that there had subsequently been an explosion.

UNIFIL immediately launched an investigation into the alleged violation of Security Council resolution 1701, which ended the 2006 war between Israel and the Lebanese group Hizbollah, and calls for respect for the Blue Line, the disarming of all militias in Lebanon, and an end to arms smuggling in the area.

“A UNIFIL investigation team is currently at the location indicated by LAF. Our effort is to ascertain if any traces of a possible explosion or other activity can be identified on the ground,” the mission stated. “At the same time, we have asked the IDF to provide us details of any incident in the area as alleged and, if so, its precise location,” UNIFIL added.

Established in 1978, UNIFIL is tasked with ensuring that the area between the Blue Line and the Litani River is free of unauthorized weapons, personnel and assets. It also cooperates with the LAF so they can fulfil their security responsibilities.

KWTX television cited West Emergency Management Services Director George Smith as confirming the death toll.

However, a spokesman for the Texas Department of Public Safety, D.L. Wilson, told Reuters the blast had resulted in “probably hundreds of casualties,” without confirming the exact number.

He added that a nearby nursing home collapsed from the explosion and that people were believed to be trapped inside.

The blast was reported at about 8 p.m. CDT (0100 GMT on Thursday) in West, a town of some 2,700 people about 80 miles south of Dallas and 20 miles north of Waco.

All the wounded have been taken to hospital and search is on for more people

Governor Rick Perry issued a statement saying: “We are monitoring developments and gathering information as details continue to emerge about this incident. We have also mobilized state resources to help local authorities. Our thoughts and prayers are with the people of West, and the first responders on the scene.”

The explosion comes two days days after the United States deadly explosions  hit the Boston marathon on Monday killing three people and wounding more than 100 others.

Syria’s deputy foreign minister, Faisal Mekdad, said none of the observers had been wounded in the blast, state TV reported. “This was a criminal act aimed at distorting Syria’s image,” it quoted him as saying.

The target was not immediately clear. The area is home to the Syrian army officers club and a building belonging to the ruling Baath Party and is also not far from the army command, according to Al Jazeera. 

Meanwhile, the rebel Free Syrian Army claimed a bomb attack in the heart of Damascus on Wednesday that it said targeted an operational meeting in a local military headquarters, according to AFP.

“The FSA operation targeted a military command office with explosives designed to go off at a meeting of army officers and members of the shabiha (pro-government militia) which decides on daily operations in Damascus,” Maher Nuwaimi, head of the FSA coordination command in Syria said.

Damascus has been rocked by several bomb blasts recently, including an attack last month at the national security building that killed three of President Bashar al-Assad’s regime members including his borther-in-law.

The latest violence comes as some Islamic countries prepare to meet in the Saudi city of Mecca to discuss the crisis. The Organisation of Islamic Co-operation is expected to suspend Syria’s membership, despite objections from Iran, Syria’s last regional ally

More than 23,000 people have been killed in violence in Syria since the outbreak of a revolt in March last year, the UK-based Syrian Observatory for Human Rights said on Tuesday.

“There were no casualties among the observers, but several Syrian soldiers were injured and taken to hospital,” the spokesperson, Ahmad Fawzi, said in response to media questions in Geneva.

The observers are serving with the UN Supervision Mission in Syria (UNSMIS), which was authorized by the Council last month, and is tasked with monitoring the cessation of violence in Syria and supporting the full implementation of a six-point plan put forward by Mr. Annan.

“[UNSMIS' Chief Military Observer] General Mood told reporters accompanying his convoy that this was an example of what the Syrian people were suffering on a daily basis and that all forms of violence must stop,” the spokesperson added.

Mr. Annan’s plan calls for an end to violence, access for humanitarian agencies to provide relief to those in need, the release of detainees, the start of inclusive political dialogue that takes into account the aspirations of the Syrian people, and unrestricted access to the country for the international media.

The crisis in Syria, which began in March 2011 as a protest movement similar to those across the Middle East and North Africa, has claimed over 9,000 lives, mostly civilians, and displaced tens of thousands.