Washington ? A large U.S. spy satellite has lost power and could hit the Earth in late February or early March, government officials said Saturday.

The satellite, which no longer can be controlled, could contain hazardous materials, and it is unknown where on the planet it might come down, they said. The officials spoke on condition of anonymity because the information is classified as secret. It was not clear how long ago the satellite lost power, or under what circumstances.

“Appropriate government agencies are monitoring the situation,” said Gordon Johndroe, a spokesman for the National Security Council, when asked about the situation after it was disclosed by other officials. “Numerous satellites over the years have come out of orbit and fallen harmlessly. We are looking at potential options to mitigate any possible damage this satellite may cause.”

He would not comment on whether it is possible for the satellite to perhaps be shot down by a missile. He said it would be inappropriate to discuss any specifics at this time.

A senior government official said that lawmakers and other nations are being kept apprised of the situation.

The spacecraft contains hydrazine – which is rocket fuel – according to a government official who was not authorized to speak publicly but spoke on condition of anonymity. Hydrazine, a colorless liquid with an ammonia-like odor, is a toxic chemical and can cause harm to anyone who contacts it.

Such an uncontrolled re-entry could risk exposure of U.S. secrets, said John Pike, a defense and intelligence expert. Spy satellites typically are disposed of through a controlled re-entry into the ocean so that no one else can access the spacecraft, he said.

Pike also said it’s not likely the threat from the satellite could be eliminated by shooting it down with a missile, because that would create debris that would then re-enter the atmosphere and burn up or hit the ground.

Pike, director of the defense research group GlobalSecurity.org, estimated that the spacecraft weighs about 20,000 pounds and is the size of a small bus.