A gas explosion in a restaurant in southern Russia during preparations for a wedding dinner has now led to the deaths of eight of the 28 restaurant workers injured in the blast.

Health officials in Russia's Dagestan region said Tuesday three more workers have died of burns suffered Aug. 1, bringing the death toll to eight, while 12 remain hospitalized.

The explosion occurred in the Layli restaurant in Makhachkala, the capital of Dagestan, before the wedding party arrived.

The gas company said its investigation showed the explosion was caused by a leak in a 50-liter (13-gallon) propane gas canister that was used for cooking. The canister was more than 40 years old and was corroded.

A criminal case was opened, but no charges have been filed.