Kolkata: At least one person was killed and several were injured when a portion of the Majerhat bridge in south Kolkata collapsed on Tuesday evening, the second such incident in two years.

Chief minister Mamata Banerjee said one person was killed, 19 people were injured and at least six were feared to be trapped under the debris. She added the state government will bear the cost of their treatment.

According to locals, a group of migrant construction workers lived under the portion of the bridge that collapsed, and rescue workers have been able to establish contact with at least four of them.

Several agencies, including the National Disaster Response Force joined the local police and fire department in the rescue operation.

The immediate priority is rescue. A threadbare investigation will be carried out to determine what led to the accident, the chief minister told the media in Darjeeling. Banerjee, who was in the hills to hold administrative review meetings, will be returning to Kolkata on Wednesday.

The Majerhat bridge was built 40 years ago. West Bengal governor Keshari Nath Tripathi blamed the state government for poor maintenance, and a political blame game started over what led to the accident.

The bridge was constructed by the Kolkata Port Trust, but officials alleged that the public works department (PWD) was responsible for its upkeep. PWD officials, in turn, blamed the railways for undermining the structural strength of the bridge. They alleged that construction of the Metro railway in the neighbourhood using heavy machinery had weakened the structure.

Meanwhile, the Rail Vikash Nigam Limited, which is constructing the Metro line/station there, said in a statement that there is no connection between the collapsed bridge and the construction of the Metro line.

In March 2016, an under-construction bridge in north Kolkata had collapsed, killing 26 people. Following the incident, the state government had undertaken a structural audit of bridges maintained by the Kolkata Metropolitan Development Authority (KMDA), said a key official, requesting anonymity. “Though the audit was conducted, it was found that KMDA did not have the necessary resources to immediately address structural deficiencies in the best possible manner," he added.