DAMASCUS, Syria (AP) — Thieves broke into Syria’s national museum and stole several ancient statues dating back to the Roman era, officials said Tuesday.

The National Museum of Damascus was briefly closed after the heist was discovered early Monday. The museum had reopened in January as the country was recovering from a 14-year civil war and the fall of the 54-year Assad family rule last year.

The country’s largest museum houses priceless antiquities. After the civil war started in March 2011, security was improved with metal gates and surveillance cameras, and authorities moved hundreds of artifacts to Damascus from around the country.

An official from Syria’s Directorate-General for Antiquities and Museums told The Associated Press that six marble statues were stolen, and that an investigation was ongoing.

Another official told the AP that the theft occurred Sunday night and was discovered when one of the doors at the classical department was found broken.

Both officials spoke on condition of anonymity in line with regulations because the government had not yet made a statement.

The police chief in Damascus, Brig. Gen. Osama Atkeh, later told state news agency SANA that several statues and rare collectibles were stolen from the museum. He said that guards there and other individuals were being questioned.

Directorate-General for Antiquities and Museums said in a statement later in the day that an investigation had been launched and that measures were taken immediately to guarantee the safety of the antiquities inside the museum. It did not say what was stolen, only saying that “some exhibits” went missing.