Middletown, Conn. – [12:55PM EST] ALL UPDATES BELOW An explosion at the Kleen Energy Plant on River Road in Connecticut has caused “mass casualties,” according to published reports.

The blast was felt for miles. All three district fire stations in Middletown responded to the scene, and Urban Search and Rescue was being dispatched Sunday.

The plant’s general manager, Gordon Holk, told CNN that the blast was responsible for casualties, but he did not provide a figure. Fire and police officials in Middletown estimated that there were indeed “mass casualties,” but no other details were immediately available, said CNN.

The explosion took place at NRG Power Plant on River Road. According to their web site they are the fossil-fueled electric generating plant in the state. The plant uses natural gas oil and ultra low-sulfur distillate fuel.

Reached by phone, plant general manger Gordon Holk told NBC CT he was enroute to the plant, and did want to speculate on the number of injured.  He said the plant is a 620 megawatt gas-fired power plant.

Reports are saying that the blast could be felt as far away as Durham.

Police are advising residents to stay in their homes.

UPDATE 2:45PM EST (Miami Herald report): 

As many as 50 people are said to have been killed in a huge explosion on Sunday at a US energy plant in Connecticut, a hospital spokesman said, adding that a search and rescue operation is underway.

“There are bodies everywhere,” one witness was quoted as saying while others said victims may be buried in the rubble of the Kleen Energy plant, which was still under construction on the outskirts of Middletown on the Connecticut River.

Officials would not immediately confirm any deaths or the number of injured.

UPDATE 2:55PM EST (Middletown Press report):

The Health Department, Red Cross, and City Hall are in the preliminary stages of setting up a family counseling center at City Hall for people who want to find out information about their friends or relatives, and for people injured from the explosion.

A source said the number of dead and injured is just speculation at this point. Emergency personnel don’t have an official number and don’t want to release a number that is too high because they do not want to worry families.

According to WTNH, at least 250 were injured. Two were dead and four were critically injured.

UPDATE 6:22PM EST (CNN Report):

Five people were killed and at least 12 were injured in an explosion Sunday at an under-construction power plant in central Connecticut, local officials said. A statement from the mayor’s office in Middletown, Connecticut, was the first official confirmation of the number of deaths in the explosion.

(WCBSTV / CNN / YWN-32 / YWN BBRY Group 3 / CT-203)