A lake at a Melbourne park has turned vibrant red after a suspected prank.

Visitors to the Carlton Gardens were taken by surprise this morning when they discovered the central lake had taken on a blood-red hue.

An aerial view of the red lake. (9NEWS)

“The lake in Carlton Gardens has turned very red,” Twitter user Denham Sadler wrote.

The bright red colour is believed to have been caused by a “non-toxic food dye” which is harmless to the environment, according to Victoria’s Environmental Protection Authority.

The lake and accompanying fountain are currently being drained and are expected to return to their normal colour by tomorrow, The City of Melbourne said in an official statement.

The incident has been reported to the police.

A river in Siberia also mysteriously turned blood red earlier this month.

Preliminary investigations found it may have been caused from chemicals which leaked from a broken pipe at a nearby nickel factory.