A 25-year-old man and a seven-year-old boy have died in separate drowning accidents at a popular swimming lake near Rotterdam.

The man died on Monday evening after leaving the part of the Zevenhuizerplas which had been marked off for safe swimming. Efforts to revive him at the scene failed, safety board officials said.

A few hours earlier, the boy had to be rescued after he too left the safe area. According to some reports, he may have been under the water for 15 minutes. Although he was taken to hospital for treatment, officials said on Tuesday afternoon that he too had died.

The local safety board has urged everyone who comes to cool off at the lake to stay within the safe area, ‘where everyone can stand up’. The lake was created by dredging for sand and is very deep and cold in places.

Note: this article was updated on Tuesday afternoon following news of the boy’s death.