A man looks at the site where a truck transporting gas exploded in Riyadh, Nov. 1, 2012. The truck transporting fuel exploded Thursday in the Saudi capital of Riyadh, killing 23 people and wounding some 135 others, Saudi state television reported. (Xinhua/Wang Bo)

Picture taken on Nov. 1, 2012 a collapsed building at the site where a truck transporting gas exploded in Riyadh. The truck transporting fuel exploded Thursday in the Saudi capital of Riyadh, killing 23 people and wounding some 135 others, Saudi state television reported. (Xinhua/Wang Bo)

People gather at the site where a truck transporting gas exploded in Riyadh, Nov. 1, 2012. The truck transporting fuel exploded Thursday in the Saudi capital of Riyadh, killing 23 people and wounding some 135 others, Saudi state television reported. (Xinhua/Wang Bo)

Firefighters extinguish a fire at the site where a truck transporting gas exploded in Riyadh, Nov. 1, 2012. The truck transporting fuel exploded Thursday in the Saudi capital of Riyadh, killing 23 people and wounding some 135 others, Saudi state television reported. (Xinhua/Wang Bo)

A man stands at the site where a truck transporting gas exploded in Riyadh, Nov. 1, 2012. The truck transporting fuel exploded Thursday in the Saudi capital of Riyadh, killing 23 people and wounding some 135 others, Saudi state television reported. (Xinhua/Wang Bo)

People inspect the site where a truck transporting fuel exploded in Riyadh, Nov. 1, 2012. The truck transporting fuel exploded Thursday in the Saudi capital of Riyadh, killing 23 people and wounding some 135 others, Saudi state television reported. (Xinhua/Wang Bo)

Local people takes photos at the site where a truck transporting gas exploded in Riyadh, Nov. 1, 2012. The truck transporting fuel exploded Thursday in the Saudi capital of Riyadh, killing 23 people and wounding some 135 others, Saudi state television reported. (Xinhua/Wang Bo)