Plant officials said the reactor automatically shut down after an instrument monitoring plant conditions transmitted wrong information to the reactor control room, The Patriot-News in Harrisburg reported Friday.One worker was injured during shutdown when he was apparently startled by the venting steam and fell, the newspaper said.A U.S. Nuclear Regulatory Commission inspector said the plant was safe. Plant officials said they were concentrating their investigation on the faulty transmission.Ralph DeSantis, spokesman for AmerGen Energy, which operates TMI, told the Patriot-News the incident happened on the non-nuclear side of the plant and did not endanger employees or the public.Plant officials could not say how long the plant will remain shut down, the Patriot-News said. Thursday's shutdown was the first unscheduled shutdown at the facility since July 1997, when the plant was down for eight days.
Three Mile Island in 1979. A reading taken from a "faulty" instrument panel on the Unit 1 reactor at the Three Mile Island nuclear power plant located near Harrisburg, Pennsylvania has caused the reactor to shut down, but officials say that there is no threat to the public as radiation has not been released into the air. A wrong reading was displayed on a control panel which triggered the reactor to automatically shut itself down.

"It appears this was an uncomplicated, smooth shutdown. The company will need to take a careful and deliberate look at what went wrong," said Nuclear Regularitory Commission spokesman, Neil Sheehan.

A worker at the power plant was injured while the reactor was shutting down, after being scared by steam venting from the reactor, which caused him to fall.

The reactor, which first went operational in 1974, shutdown on Thursday afternoon on the "non-nuclear side of the reactor" at 1:35 p.m. EST and as of the moment remains offline, added Sheehan. This is the first time since 1997 that the reactor has shutdown.

In 1979, the Unit 2 reactor suffered a partial meltdown and has remained offline since the disaster.