“The blast was very strong. It shook the city. But the reason behind the blast is still unknown,” Fars said, without quoting a source.
Tabriz is the capital of Iran’s Northeastern Azerbaijan province.
“The windows of many buildings were shattered from the blast,” the agency said.
Iran often blames blasts in outlying provinces on foreign agents.
The majority of the population in Tabriz are Azeris and speak a language closely related to Turkish. They make up about 25 percent of the population in the Islamic Republic of Iran.
http://www.iht.com/articles/reuters/2008/02/25/africa/OUKWD-UK-IRAN-EXPLOSION.php
Explosions almost appear to be routine. But, this one was larger?
Maybe some Israeli jets dropped some ordnance.