[originaltext]　　At least 10 people have died in the American state of Texas aft

　　At least 10 people have died in the American state of Texas after (3)a bus carrying 15 prisoners and prison staff skidded off an icy bridge on Wednesday morning. Kim Ghattas is in Washington. "The bus was carrying 12 prisoners who were being transferred from one prison to another in Texas; also on board was three correction officers. The white bus was almost half way through its 6-hour journey from Abilene to El Paso on the border with Mexico. It slid on the icy roads at 7:30 in the morning just west of the town of Odessa, slipped down in an embankment and then hit a freight train before landing on its side. (4) Eight prisoners and two correction officers died. The other five passengers were injured and taken into hospital. "
　　3. How did the accident happen?
　　4. How many prisoners died?