The young girl died, and the second is in critical condition after the tree fell to the Essek Marine Park on Saturday.
The girls, seven and six, suffered severe injuries and were taken to the hospital. The police said the 7-year-old girl died in the hospital.
Three other children suffered less injuries after the incident in the southeast at sea.
Essek police said they called them in Chalkclell Park in a little before 3:00, where they found “numerous victims”.
Ch Subt Leighton Hammett said, “Families face unimaginable difficulties tonight and all our thoughts are at the moment.
“I can’t start saying words how hard events are today and continued to be for them.
“I also not lost me on me how much it had to be for public members who witnessed this awful incident.”
The Emergency Service in Eastern England said earlier, “Two children were transported to the University Hospital of Southend.
“Further three children later were transported the way to the same hospital with minor injuries.”
Police advised the public to avoid the area.
Adam Hutchins, 47, said Essekle Web site: “I heard the kids played on the tree. They heard a big crack.
“It must have been (either) pretty. They crossed and there were children under the tree.
“All cricket guys transferred and tried to tap the wood above. I think it’s one of the oldest trees. She had metal stands.”
David Burton-Sampson, the work of the MP for Southend Vest and Leigh, described it as a “worrying incident”, adding, “My thoughts are with those affected.”
Daniel Covan, the leader of the city council Juardend, said on Saturday: “I’m aware of this very serious incident. We work with Essex Police, the Emergency Service and Fire Department, who are still at the scene.
“I understand that the tree fell, there are a number of victims and we are just looking for the public to avoid the area while those services perform their work and my thoughts are with those affected.”
