"At 7:15 in the morning, while we were sleeping in our houses, we heard a big blast. We went outside and saw the bridge had collapsed," Sa'd al-Khaza'li, an man living near the bridge, told Reuters in Baghdad today.
"We went to try and save people, to save our brothers there, but we found no one. Only the damaged bridge, and no one was there."
Rescue teams are searching for survivors in the water.
Iraqi security officials on the scene said the truck was parked in the middle of the bridge when it exploded.
The Tigris River cuts Baghdad in half and the Al-Sarafiyah Bridge is a key artery in the northern part of the city. It is often used by minibuses and commercial vehicles travelling from central Baghdad to markets in the city's northern areas.
(compiled from agency reports)