At least two people were killed and four are missing following an explosion Monday at a gas refinery near the Italian city of Florence, according to local authorities.

A further nine people were injured in the blast at the facility, which belongs to Eni, one of the largest energy companies in Italy.

A fire caused by the explosion is now under control, according to the local municipality of Calenzano.

“Eni confirms that a fire broke out this morning at the fuel depot in Calenzano,” the company said in a statement, adding that the fire was confined to a loading area and did “not affect the tank farm in any way.”

“The impacts and causes are being immediately verified,” Eni said.

The regional Department of Civil Protection issued an alert for the area within 5 kilometers (3 miles) of the explosion, warning residents to “keep windows closed and do not go near the area.”

“All of Tuscany is united in grief for the tragedy that happened today in Calenzano,” regional president Eugenio Giani said on Telegram.

The local municipality has declared two days of mourning on Monday and Tuesday.

This is a developing story and will be updated.