Children were seen playing in a lake just hours after two teenagers died and four others were rescued.
It comes search and rescue officials pulled the bodies of two young men, aged 18 and 19, from a lake at the High Eske Nature Reserve in East Yorkshire on Wednesday afternoon while another two were rescued.
Humberside Fire and Rescue service reported that the area would be closed off during the day while investigations continued and advised people to stay away from the water.
But members of the public said there was no obvious sign of anybody there - or any signs stopping people from accessing the area or swimming, reports Hull Live.
One woman at the lake said: "I've been here all day and I thought that the news couldn't be true. There's not a single 'no swimming' sign or bit of police tape up.
"Kids have been swimming in the lake, and they had no idea something had just happened. There hasn't been anyone from the emergency services down here that I've seen.
"It's a sad and shocking tragedy. I can't believe nobody is here to warn people."
In a statement issued earlier this afternoon, Humberside Fire and Rescue said: "The Service is working closely with Humberside Police, and the area is currently closed to the public as we continue to investigate this very tragic incident.
"The Service would like to stress the importance of remaining safe around open water and the clear advice from the Emergency Services is that people should not enter the water.
"Open water such as ponds, rivers and lakes etc. are highly dangerous and people should not enter them."
However, it's since been made clear that the service does not have the means to physically close the area, and people are advised not to go in the water.
The circumstances of the tragedy are now under investigation.
Superintendent Paul Butler of Humberside Police, said: "Our thoughts and condolences are with both young men’s families and loved ones at this very difficult and sad time.
"We are working together with all the relevant agencies including Humberside Fire and Rescue services, to fully understand the circumstances of the tragic accident."
Humberside Fire and Rescue said: "Last night Emergency Services attended an incident at High Eske Nature Reserve, Tickton, despite the very best efforts of the emergency services on the scene, tragically the incident resulted in two young people losing their lives.
"Crews from Humberside Fire and Rescue Service, Humberside Police, and Yorkshire Ambulance Services were in attendance and worked together.
"A further four members of the public were rescued from the reserve by Humberside Fire and Rescue Service using a boat and Humberside Police deployed diving teams.
"Our thoughts and deepest sympathies are with the families and friends at this difficult time."
