Pune | Four persons died and 18 were seriously injured after an old iron bridge on Indrayani river collapsed on Sunday afternoon in Pune's Maval tehsil, officials said.

While two persons succumbed to injuries during treatment after being rescued, the bodies of two persons were recovered from underneath the collapsed portion of the bridge, officials said.

"While two bodies were recovered from beneath the structure, we suspect one person is trapped there. Efforts are underway to locate and rescue the person," Talegaon Dabhade police station senior inspector Pradeep Rayannawar said late evening.

The incident took place at 3:30pm in Kundamala area, which has been seeing heavy rains over the past few days, giving the river a steady flow, another official said. It was not raining when the bridge collapsed in the presence of at least 100 picnickers, he added.

"In the mishap, so far 38 people have been rescued of which 18 sustained serious injuries and they are currently under treatment in three different hospitals. During treatment, two people succumbed to injuries," a statement from the district administration informed.

Teams of the National Disaster Response Force (NDRF), a specialised unit to tackle such emergencies, as well as personnel from the fire brigade, police and local rescue organizations are involved in rescue and relief efforts, it added.

Maharashtra Minister of Disaster Management Girish Mahajan, who was at the site monitoring rescue efforts, said the bridge collapsed under the weight of a large number of tourists.

"The bridge was meant only for pedestrians and there was a warning board there stating that it cannot be used by two-wheelers. It seems people on the bridge did not pay heed to these instructions, which caused the incident," Mahajan told reporters.

He said the state government has announced compensation of Rs 5 lakh each to the kin of the deceased.

Queried about the lack of police presence at the spot despite it attracting crowds amid rains, the minister said this would be probed.

"'It has been observed that despite giving constant warnings about dangerous spots during the monsoon, people go and risk their lives. We appeal to the tourists not to risk their lives by visiting such places," he added.

Speaking about rescue and relief efforts, Mahajan said cranes have been deployed to remove the collapsed portion of the bridge, while full scale efforts are on to rescue some people stuck under this collapsed part.