A major incident has been declared over what police have called a sinkhole at a canal in Shropshire, leaving boats either stricken in a gaping cavity or teetering on the edge of a steep drop.

Pictures appear to show that the structural integrity of a stretch of waterway in the Chemistry area of Whitchurch has completely given way, raising flooding fears.

Two narrowboats are said to have sunk into the hole, into which water looks to have drained completely. Another two are at the edge.

Shropshire Fire and Rescue Service said it was responding to a landslip and confirmed a canal was affected. There are no reports of casualties, according to West Mercia Police.

The force asked people to avoid the area and seek alternate routes.

It added that people on other parts of the waterway nearby were being supported by fire crews.

The Canal and River Trust described the incident as a breach on the canal, and said its priority was the safety of boaters and those in the immediate area.

“We are carrying out initial investigations into the possible cause of the breach and will provide more details in due course,” it said.

“We will also seek to return water levels either side of the breach as soon as possible and are providing support to the boaters affected and those in the immediate area either side of the breach.”

Andy Hall, a councillor in Whitchurch, said the incident unfolded at about 05:00 GMT.

“We’ve got two boats at the bottom of the sink hole that have fallen down, and we’ve got two boats that are teetering on the edge that could go in at any time,” he told the BBC.

“Obviously [the fire service is] going to make those safe.”

He added: “[People] thought that there was an earthquake.

“To the right, we’ve got the field which has taken probably about a million gallons of water out of the canal.”

He said the fire service had put in a flood gate to stop the flow of more from the compromised waterway.

“The most important thing is that the canal itself has been secured by fire and rescue. Their biggest worry was that the canal was going to burst even more and flood residents in the town,” he said.

He added that contrary to speculation on social media, there had been no bridge collapse.