A baby boy has died after being found unresponsive in a lake at an overnight rest stop area, with police investigating the child’s “unexplained” death.

Police and paramedics were called to Chatsworth Park, a free campground area off Gympie-Curra Rd in Gympie, about an hour north of the Sunshine Coast, at around 10.30am on Saturday.

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A seven-month-old boy was found unresponsive in a nearby lake, with the child pulled from the water by his mother.

Multiple people were also at the rest stop area at the time and jumped in to perform CPR before paramedics arrived.

The child was taken to Gympie Hospital in a life-threatening condition where he died later that night.

His family had camped at the park overnight and were on their way back home to North Queensland, Detective Inspector Craig Mansfield said on Monday.

Their campsite was located about 40m to 50m from the water’s edge.

Mansfield said the child’s death is being treated as “unexplained”.

Detectives from the homicide squad and the Child Trauma Unit are assisting local officers to investigate how the child came to enter the water.

Campers who left the park shortly after the incident could help investigators piece together exactly what happened, Mansfield said.

“We’re just working on how this has occurred so those additional people coming forward might fill those very gaps,” he said.

“We have part of the picture we just want to complete that full picture before we decide on where the investigation leads us.”

A post-mortem will be conducted on Monday morning to establish if the child had suffered any other additional injuries.

Part of the park remains a crime scene.

Anyone who witnessed the incident, or has any information, has been urged to contact police.