A part of the reinforced concrete "retaining wall" along the Burdwan-bound lane of a flyover on NH19 in East Burdwan collapsed on Wednesday morning when vehicles were on the flyover.

However, the vehicles escaped damage, which officials described as "fortunate".

A part of the retaining wall built over a raised channel filled with earth, near Sardanga of Memari, tumbled, its impact causing the edge of the adjoining road to cave in.

Police immediately halted traffic to prevent any mishap as a shower of debris from the broken wall fell on the service road below and the edge of the flyover lane partially gave way.

NH19, formerly called the Delhi–Calcutta Road, is one of the busiest national highways. After the renumbering of national highways, the Delhi-Agra route is now NH44 and the Agra-Calcutta route is NH19.

According to police sources, debris was noticed by two civic volunteers, Sheikh Bappa and Nikhilesh Das, who were on traffic duty on a service road beneath the bridge.

Before they could alert their superiors and approaching motorists, a stretch of nearly 50 metres of the wall collapsed. Vehicles were still moving on the flyover.

“Around 10am, we were managing traffic on the service road when we suddenly heard an unusual sound and looked up to the flyover. We saw debris from the retaining wall falling. Fearing something serious, we rushed towards the flyover. But before we could reach, the wall began collapsing in front of our eyes. We stopped traffic and informed senior police officers,” Sheikh Bappa told reporters.

Police and engineers from the National Highways Authority of India (NHAI) reached the spot and stopped traffic on the damaged part of the Burdwan-bound lane "indefinitely". Vehicles were diverted through a nearby service road to maintain connectivity along the busy highway corridor.

The collapse has raised eyebrows as the six-lane expansion of the NH19 stretch had been completed barely a year ago. The flyover became operational only six months ago.

Residents alleged negligence by highway authorities and claimed that materials of poor quality were used during construction.

Officials of the NH19 project office in Burdwan declined to comment on the matter, stating they were not authorised to speak to the media.

A project official, requesting anonymity, said traffic on the vulnerable portion had been completely suspended to prevent further damage to the structure.

“To avoid additional stress on the weakened section, traffic has been stopped on the Burdwan-bound lane and vehicles are being diverted through the service road from Ajhapur crossing,” he said.

“Our senior engineers will conduct a detailed examination of the damaged stretch and prescribe repair work. It may take around one month for normal traffic movement to resume,” he said.

To minimise inconvenience to motorists, the police have put up diversion signages ahead of the affected stretch and deployed personnel to guide motorists to the detour.