(CNN) -- At least seven people were killed Wednesday when a Polish military transport aircraft carrying passengers who had attended a flight-safety conference crashed in northwest Poland, military officials said.
Defense Ministry Col. Cezary Siemion confirmed seven deaths, but said that number could continue to climb.
He said there were 18 people on board -- 14 passengers and four crew members.
The Spanish-built CASA transporter crashed near the town of Miroslawiec, a few hundred kilometers northwest of Warsaw, around 7 p.m. (noon ET).
The passengers had attended the 15th annual Flight Safety Conference, held in Warsaw on Wednesday.
Officials said it was the first accident in Poland involving a CASA transporter, which is generally considered an extremely reliable aircraft.
The airplane took off from Warsaw and was scheduled to make stops in three cities before returning to its home base in Krakow. It crashed before reaching its second destination.
Military officials said a special commission has been set up to investigate the crash and rescue operations are ongoing. E-mail to a friend