A powerful explosion hit a large market in the Armenian capital of Yerevan on Sunday, starting a fire and killing at least 15 people.

62 people were reported injured. Some 18 people were still missing, according to local authorities.

Firefighters labored for hours after the early afternoon blast at the Surmalu market to put out the blaze.

Later Sunday, Armenia was reeling from a series of bomb threats targeting metro stations, and unspecified significant military and civilian facilities.

What do we know so far?

The blast happened at a building where fireworks were stored. It is thought the pyrotechnics were being stored incorrectly, but there was no immediate indication of what caused them to ignite.

Fireworks continued to explode, even as rescue workers and volunteers in civilian clothes searched amid thick smoke and dust in the air. 

Posts on social media showed a thick column of black smoke above the market, with successive detonations audible.

At least three people were reported to have been rescued from beneath the debris.  

It was not immediately clear what caused the fireworks to detonate.

The open-air market, some two kilometers (over a mile) south of the Yerevan's city's center, is popular for its low prices and a wide variety of merchandise. 

A former Soviet republic in the South Caucasus, Armenia is one of the poorest countries in the region and safety regulation violations are commonplace.

ar, rc/jcg (Reuters, AFP, AP)