London (CNN) -- Four miners are trapped in a coal mine in Swansea Valley, South Wales, police confirmed Thursday.
Rescue services are at the scene at Gleision Colliery, a police spokeswoman told CNN.
Seven men were in the mine when the incident occurred, and emergency services were called soon after 9 a.m. local time (4 a.m. ET), the spokeswoman said.
Three of them got out of the mine and one has been taken to the hospital, she said, but his condition is unknown. Two of those who escaped made their way out unaided before emergency crews arrived.
Local police Superintendent Phil Davies told reporters it was too early to say what had caused the incident but confirmed that water was present within the mine, which he described as a small, privately-owned operation.
"We are dealing with a difficult rescue operation, therefore that does take time, but we are doing everything possible ... to get these men out," he said at a televised news conference.
Mine rescue officer Andrew Watson told CNN that no contact had been made with the trapped men but that rescuers hoped they were in a pocket of air below ground.
He said water was believed to have rushed into the mineshaft where they were working when they broke into a neighboring abandoned mine. Pumps are being used to reduce the level of the water, he said.
Specialist rescue workers are currently exploring underwater to try to find out what has happened to the trapped men, Watson said.
The men who escaped have given information on where the four miners were working at the coal face before the water rushed in, he said, but rescuers cannot be sure of their location now and access to communications technology within the mine is limited.
Families and friends of those affected have been informed, Davies said, and the two men who escaped on their own were providing information to the emergency services.
A team with specialist equipment for carrying out rescues in confined spaces is also at the scene, a joint statement from the South Wales emergency services said.
Local lawmaker Gwenda Thomas, who represents the Neath constituency in which the mine lies, near Cilybebyll, issued a statement saying she was heading back to the area.
"I am currently travelling back to Rhos community center from Cardiff. My thoughts are with all the family and friends of those currently trapped in the mine and I have confidence in all the emergency services at the scene."
A spokesman for Thomas, Robert James, told CNN the colliery was one of the few remaining drift mines operating in the area.
In a drift mine, coal is excavated from the side of a hill using shafts that are almost horizontal.
CNN's Laura Smith-Spark contributed to this report.