Tehran, March 12 (IANS): At least seven people were killed in the northwestern Iranian province of Ardabil in a firework blast, media reported on Saturday.

The explosion occurred in a residential building in a district in Ardabil a few days before the Chaharshanbe Suri -- the Iranian festival of fire, Xinhua cited Press TV that quoted Ardabil's chief prosecutor, Nasser Atabati, as saying.

The explosion happened due to the carelessness of a teenager while he was producing handmade fireworks and explosives inside the residential building.

Some materials used for the production of explosives were found beneath the rubble, Atabati said.

The teenager and six other family members were killed and four others were injured.

Chaharshanbe Suri is an Iranian festival celebrated on the eve of the last Wednesday before Iranian new year or Nowruz.

During the Chaharshanbe Suri celebrations, Iranians traditionally jump over bonfires and set off firework.

This year's Nowruz falls on March 21.