An investigation has been launched after hundreds of fish were found dead in Linlithgow’s historic lake.

Footage from the lake shows large amounts of dead fish in the water near the outflow pipes of the nearby Kingsfield estate.

The Scottish Environment Protection Agency (Sepa) said it attended the site on Tuesday, following the discovery on Monday night.

The environmental watchdog is trying to discover whether pollution was the cause of the mass murder.

Linlithgow Loch Fisheries secretary Tom Lambert told BBC Scotland News he had never seen such a shocking sight.

Although the lake was stocked with rainbow trout, a large swarm of roach native to the lake had been killed, he said.

“A poisonous substance must have come from the pipe since it killed all the young cockroaches sheltering at the exit,” he said.

“Many members of the public don’t realize that if they throw things down the drain, they could end up in the lake.”

Some of the fish were also lying on the grass beyond the pipe outlet.

“They were trying to escape the toxic substance and ended up on the grass, it’s scary,” he said.

Mr. Lambert took a boat to the middle of the lake and found more dead cockroaches there.

“I’m very sad and disappointed that this happened,” he said. “This has been happening for years, it’s not this big of a fish kill but nothing seems to be being done about it.

“They haven’t diverted the pipes. They don’t want to spend the money, so it’s more convenient to dump them directly into the lake.”

The lake attracts special attention and is a major tourist attraction.

Located next to the lake, Linlithgow Palace is the birthplace of Mary Queen of Scots and James V. It has been described as Scotland’s finest surviving late medieval secular building.

Mr Lambert asked Historic Environment Scotland, which owns the site, to send a ranger to remove the fish but was said to have been advised by Sepa to abandon them until the investigation was completed.

A spokesman for Historic Environment Scotland said: “We continue to work closely with Sepa as we conduct an investigation.

“Our rangers are monitoring any further changes and, as a precaution, we advise the public to avoid the area in question while further investigation is carried out.”

There are now concerns that other wildlife could be poisoned by eating the fish that were still there on Friday.

A spokesman for Sepa said: “We received reports of a number of dead fish being found in Linlithgow Loch on 11 November and officers attended the site the following day.

“We continue to work with our partners as we investigate the potential causes of the incident.”

A Scottish Water spokesman said: “We have found no problems with any of our infrastructure in the area but we will assist Sepa with any investigations carried out.”