At least 26 people have been killed and more are feared missing after a railway bridge under construction collapsed in north-eastern India, officials said.

The incident occurred near the town of Sairang, in the state of Mizoram.

Up to 40 workers were at the site when part of the bridge collapsed, according to local media reports.

The cause of the incident is not yet clear and the railway authority has opened an investigation. Three people have so far been rescued.

That includes an injured worker who had to be brought down from the top of one of the bridge's 100m-high (328ft) pillars.

The incident happened over the Kurung River, about 20km (12 miles) from the city of Aizawl, Mizoram's capital.

"All possible assistance is being given to those affected," said Prime Minister Narendra Modi's office in a statement.

The government will pay some 200,000 rupees (£1,900; $2,400) to the next of kin of those killed, it added.

The victims are all from West Bengal, according to railway officials.

"Words cannot express the depth of sorrow and sympathy for the families affected by this tragic event," said Mizoram's Home Minister Lalchamliana.

The Khamrang-Sihhmui railway line will be 51km long and is due to be completed in December after work began nearly two years ago.

Accidents on these kinds of construction sites are not uncommon in India.

In October last year, more than 140 people were killed when a pedestrian suspension bridge collapsed in India's western state of Gujarat.