An open exercise book with a page full of cricket scores lay atop a school bag on the floor of the bus.

A solitary shoe rested on a seat next to a lunchbox with its lid missing. A water bottle that had rolled down the floor lay there with its snout open. The stairs were covered with shards of blue tinted glass. The ceiling had dents, and some of the rear seats had come loose.

To anyone who entered the overturned school bus of Delhi Public School Megacity after it was brought back on its wheels on Thursday afternoon, it would have been hard to believe that those who were inside — 31 students and a teacher — escaped without critical injuries.

“Luck saved them. A lamppost acted as a buffer even as the bus overturned after hitting the median divider. Had it toppled over to the opposite lane, vehicles speeding down the other flank would have rammed into the bus. I shudder to think what would have happened then,” recounted Sahidul Islam, who witnessed the accident.

The driver of the bus, ferrying children home to localities along VIP Road and its nearby areas, was apparently not at fault.

“A preliminary investigation suggested that the driver of the school bus slammed the brakes to avoid colliding with the minitruck running in front after it had hit a motorcyclist. As the bus swerved and rammed the divider and overturned, a Chevrolet Spark hit it from behind. Fortunately, there was no pile-up,” said a senior police officer of North 24-Parganas.

The minitruck that apparently triggered the accident sped away.

As the bus stood on its roof, tyres still whirring, people who were at work in the nearby construction sites rushed to the rescue of the children trapped inside.

“Clinging to their seats, the children were screaming for help. We smashed the rear windshield and dragged them out, one by one,” said Hafizul Islam, a supplier of construction materials.

A car carrying four air hostesses to the airport picked up two of the injured students and took them to Charnock Hospital, off VIP Road.

Alerted by the air hostesses, the hospital sent an ambulance to pick up the rest of the injured.

Subrata Mondal, who was in a nearby tea stall, said the cries of children rent the air as he and the other rescuers waited for help to arrive.

“All the children were in shock. Most of them seemed to have suffered only cuts and bruises, though we couldn’t be sure there were no critical injuries until they received medical attention. So until the ambulance arrived,we made them sit on the divider and tried assuring them they would be fine,” said Mondal.

A doctor at Charnock Hospital confirmed that none of the children was critically injured. Schoolteacher Suman Duggal, 29, suffered spine, head and shoulder injuries but was discharged in the evening.

Motorcyclist Sankar Jana, a resident of Alipore working in an IT services company, suffered a fractured left wrist and was admitted to the ICU for suspected head injuries.

Some of the children, including injured Teghoria resident Ayush Jain, were escorted home by strangers before the ambulance arrived. Some passers-by offered their cellphones to students to contact their parents.

“It was heartening to hear about passers-by and people working in the construction sites helping the injured students through this ordeal. Nowadays even cars passing by don’t stop when an accident occurs,” said the parent of an injured student.

A payloader was used to haul up the overturned bus and clear the road. The lamppost that saved the vehicle from toppling over stood its ground, but its shade lay smashed to smithereens, next to a piece of blood-stained cloth.